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A CASCA Emerging Researchers Showcase

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Description

We are excited to announce the “CASCA Emerging Researchers Showcase”,  a virtual symposium featuring presentations from early career researchers - undergraduates, graduate students, and postdoctoral fellows - across our community. This event is scheduled for October 28, 2026, is completely free of charge, and will be held entirely online.

Registration is open to all. Abstract acceptance is now closed, and participants have been informed of abstract decisions.

Event highlights include scientific talks based on selected abstract submissions from our emerging researchers; a dedicated 1-hour interactive poster session; a career development discussion focused on the postdoctoral and/or industry job market and lessons learned from the GAAP and GAAP-II workshops organized by the Graduate Student Committee; and a facilitated mentoring/social interaction session.

A Special Call to Colleagues in Permanent Positions at Universities and Research Institutes: 

  • Please mark your calendars and plan to attend the CASCA Emerging Researchers Showcase. Your feedback shapes the next generation. Our students and postdoctoral fellows prepare extensively for these presentations. Your constructive questions and engaged discussions provide the professional development they need.

  • The dedicated 1-hour poster session is a prime opportunity for you to interact directly with students and postdocs and learn about the accomplishments of our early career colleagues.

This Showcase serves a dual purpose: not only will it highlight the excellent research of our trainees, but it will also act as a critical technological and logistical dry run for our virtual Annual General Meeting (AGM) next summer. As such, we need a realistic audience size to evaluate platform capacity, audio/video quality, and interactivity features. The active participation of many attendees will help us test platforms, refine our scheduling, and ensure a smooth experience for the larger meeting.

Event Highlights (October 28)

Scientific Talks: Oral sessions featuring selected abstract submissions from our emerging researchers.

Poster Session: A dedicated 1-hour interactive poster session (a key opportunity for dialogue between early career researchers and more experienced colleagues).

Career Development Workshop: A discussion focused on the postdoctoral and/or industry job market and lessons learned from the GAAP and GAAP-II workshops organized by the Graduate Student Committee.

Facilitated Networking: The chance to meet and get to know new colleagues from across the country!

Key Information & Deadlines:

Abstract Submission Form: https://nyx.physics.mcgill.ca/event/587/abstracts/ 

Abstract Submission Deadline: September 28, 2026

Full Schedule Announcement: October 14, 2026

Preliminary Block Schedule (at a glance): https://bit.ly/CASCAEmergingResearcherVM

We will use Hyhyve to accommodate talks, posters, and interactive discussions. We will give instructions on how to use the platform prior to the meeting.

How to Participate

For students and postdocs: submit an abstract via the form linked above and gain valuable presentation experience at the CASCA Emerging Researchers Showcase [now closed]. You can register without submitting an abstract, if desired. 

For colleagues in senior positions: simply attend and engage! Formal registration is required; please go to the registration page.

For Everyone: Help us test the waters for the AGM—your feedback on the platform experience will be collected after the event.

Participants are expected to follow the CASCA Code of Conduct, found here.

We look forward to a vibrant, interactive day of scientific exchange. 
 

Nous sommes heureux d’annoncer le « CASCA Emerging Researchers Showcase », un symposium virtuel mettant à l’honneur les présentations de chercheuses et chercheurs en début de carrière — étudiantes et étudiants au premier cycle, aux cycles supérieurs et chercheuses et chercheurs postdoctoraux — de partout au sein de notre communauté. L’événement aura lieu le 28 octobre 2026, sera entièrement gratuit et se tiendra exclusivement en ligne (la plateforme sera confirmée prochainement).

L'inscription est ouverte à tous. La soumission des résumés est close et les participants ont été informés des décisions les concernant.

Parmi les activités prévues : des présentations scientifiques sélectionnées à partir des résumés soumis par nos chercheuses et chercheurs en début de carrière; une séance d’affiches interactive d’une heure; une discussion sur le développement de carrière portant sur le marché de l’emploi postdoctoral et/ou industriel, ainsi que sur les leçons tirées des ateliers GAAP et GAAP-II organisés par le Comité des étudiants diplômés; et une séance animée de mentorat et d’interactions sociales.

Appel spécial aux collègues occupant des postes permanents dans les universités et les instituts de recherche:

  • Nous vous invitons à réserver la date et à participer au CASCA Emerging Researchers Showcase. Votre rétroaction contribue à façonner la prochaine génération de chercheuses et chercheurs. Nos étudiantes, étudiants et chercheuses et chercheurs postdoctoraux consacrent beaucoup d’efforts à la préparation de ces présentations. Vos questions constructives et votre participation active aux discussions leur offriront une expérience essentielle à leur développement professionnel.
  • La séance d’affiches interactive d’une heure constitue une excellente occasion d’échanger directement avec les étudiantes, étudiants et postdoctorantes et postdoctorants, et de découvrir les travaux et réalisations de nos collègues en début de carrière.

Cette vitrine poursuit un double objectif : non seulement mettre en valeur l’excellence des travaux de recherche de nos chercheuses et chercheurs en formation, mais également servir de répétition technique et logistique pour l’assemblée générale annuelle (AGA) virtuelle de l’été prochain. Nous avons donc besoin d’un nombre réaliste de participantes et participants afin d’évaluer la capacité de la plateforme, la qualité de l’audio et de la vidéo ainsi que les fonctionnalités interactives. La participation active d’un grand nombre de personnes nous aidera à tester les plateformes, à perfectionner notre programmation et à assurer le bon déroulement de la réunion de plus grande envergure.

Activités principales (le 28 octobre)

Présentations scientifiques: séances de présentations orales mettant à l’honneur des résumés sélectionnés parmi les soumissions de nos chercheuses et chercheurs en début de carrière.

Séance d’affiches: une séance d’affiches interactive d’une heure, offrant une occasion privilégiée de dialogue entre les chercheuses et chercheurs en début de carrière et leurs collègues plus expérimentés.

Atelier de développement de carrière: discussion consacrée au marché de l’emploi postdoctoral et/ou industriel, ainsi qu’aux leçons tirées des ateliers GAAP et GAAP-II organisés par le Comité des étudiants diplômés.

Réseautage: une occasion de rencontrer de nouvelles personnes et de faire connaissance avec des collègues de partout au pays!

Informations importantes et dates limites:

Formulaire de soumission des résumés:
https://nyx.physics.mcgill.ca/event/587/abstracts/

Date limite de soumission des résumés: 28 septembre 2026

Publication du programme complet: 14 octobre 2026

Programme préliminaire (aperçu):
https://bit.ly/CASCAEmergingResearcherVM

Nous utiliserons Hyhyve pour accueillir les présentations, les posters et les discussions interactives. Nous fournirons des instructions sur l'utilisation de la plateforme avant la réunion.

Comment participer

Pour les étudiantes, étudiants et chercheuses et chercheurs postdoctoraux: soumettez un résumé au moyen du formulaire indiqué ci-dessus et profitez de cette occasion pour acquérir une précieuse expérience de présentation. Vous pouvez également vous inscrire sans soumettre de résumé, si vous le souhaitez.

Pour les collègues occupant des postes permanents: il vous suffit de participer et de prendre part aux échanges! L’inscription officielle est obligatoire; veuillez utiliser la page d’inscription.

Pour tout le monde: contribuez à la préparation de l’AGA en nous aidant à tester la plateforme. Vos commentaires sur votre expérience avec celle-ci seront recueillis après l’événement.

Les participantes et participants doivent respecter le Code de conduite de la CASCA, disponible ici :
 

Nous avons hâte de vous retrouver pour une journée dynamique et interactive consacrée aux échanges scientifiques.

On behalf of NLOC27
Renée Hlozek (Chair)
Theodore Grosson (Co-Chair)
Alice Curtin (Co-Chair)
Aarchi Shah
Bhuvan Manojh
Chris Matzner
Dennis Crabtree
Ivana Damjanov
Jeremy Favaro 
Karun Thanjavur

 

Registration
Registration for the CASCA Emerging Researchers Showcase
Register
Alice Curtin on behalf of NLOC27
    • 11:30 → 12:00
      Networking: Welcome
    • 12:00 → 12:30
      Plenary
    • 12:30 → 12:45
      Bio break
    • 12:45 → 14:15
      Black holes & Instrumentation: Full contributions
      • 12:45
        Early Black-Hole Growth Constraints from JWST 10m

        Aims. Massive black holes in the early Universe had limited time to assemble. We identify which JWST black-hole candidates place the strongest constraints on early growth models and assess how these constraints depend on mass estimates and growth assumptions. Methods. We compile 350 published measurements at $z\geq4$ and analyse a primary sample of 220 objects with broad Balmer-line masses. An expanded sample adds 13 tentative or conditional Balmer-line candidates and GN-z11, whose mass is inferred from ultraviolet lines. We propagate reported mass uncertainties and test mass-scale shifts and alternative growth assumptions. Results. For $100\,M_\odot$ seeds formed at $z=30$, radiative efficiency $\epsilon=0.1$, and no merger boost, 8 of the 220 objects require a lifetime-average Eddington ratio $\overline{f}_{\mathrm{Edd,req}}>1$. Five exceed unity in at least 95% of Monte Carlo draws using the reported mass uncertainties. For UNCOVER-20466, COSMOS3D-13852, and RUBIES-EGS-55604, at least 95% of draws still require an average Eddington ratio above 1 after reducing each mass by $0.5$ dex (a factor of approximately 3.2). Delaying seeding to $z=20$ gives GN-z11 the highest required average Eddington ratio. At $\epsilon=0.05719$, the ideal thin-disc efficiency for a non-spinning black hole, all 234 central mass estimates are reachable from $100\,M_\odot$ seeds formed at $z=30$ without lifetime-average accretion above the Eddington limit.

        Speaker: Nicole Jiang (University of Toronto)
      • 12:55
        Little Red Dots from Primordial Black Holes 10m

        Recent JWST observations of distant luminous galaxies and compact "little red dots" suggest the existence of early supermassive black holes (SMBHs) with masses $> 10^5\,M_\odot$. Their rapid emergence challenges conventional seeding and growth scenarios, motivating the question: could these SMBHs be seeded by primordial black holes (PBHs) formed from inflationary perturbations?
        Explaining such massive seeds requires primordial power spectrum enhancements that are stringently constrained by cosmic microwave background (CMB) spectral distortions. In this work, we perform the first comprehensive exploration of the parameter space capable of producing SMBH-mass PBH seeds while remaining consistent with CMB $\mu$-distortion constraints. We adopt a model-independent approach, and allow for an arbitrary amount of local-type non-Gaussianity.
        Our results delineate the viable region of early Universe parameter space that can reconcile the JWST high-redshift SMBH population with inflationary theory, and highlight that next-generation CMB spectral distortion telescopes will be capable of testing much of this space in the near future.

        Speaker: Dario Lorenzoni (University of Manitoba)
      • 13:05
        Inferring the Black Hole and Accretion Parameters of Sagittarius A* from EHT Observations Using a Semianalytic Model 10m

        The Event Horizon Telescope (EHT) Collaboration produced the first image of the apparent shadow of the central black hole of Sagittarius A$^*$ (Sgr A$^*$). Sgr A$^*$ source structure varies significantly on timescales shorter than the duration of an observation, preventing improved data coverage through Earth rotation aperture synthesis. This rapid variability provides the opportunity to quantify intrinsic variability and separate time-variable emission features from stable signatures of strong gravity and the accretion environment. To infer unknown properties of Sgr A$^*$ and its surrounding accretion flow, we perform Bayesian inference on a series of EHT data segments ("snapshots"). We directly fit parameters of a semianalytic emission model jointly with complex station gains to snapshot visibilities, then extract estimates of the time-averaged, persistent source structure and temporal variability by stacking snapshots in a Bayesian hierarchical model. This approach successfully reproduces parameters of general relativistic magnetohydrodynamic simulations using synthetic EHT observations. Even with physically motivated assumptions about the Sgr A$^*$ environment, black hole spin and magnetic field parameters are poorly constrained by 2017 EHT observations. Our inference constrains other parameters, favoring a nearly face-on observer inclination ($\theta_{\rm o} = 9.2^\circ \pm 3.6 ^\circ \pm_{\rm v} 11.6^\circ$), an emission peak near the horizon ($R_{\rm peak} = 4.9 \pm 0.1 \pm_{\rm v} 0.5\,GM/c^2$), near-northern projected spin position angle ($p.a. = 7.3^\circ \pm 7.08 ^\circ \pm_{\rm v} 43.5^\circ$ counterclockwise from vertical), and dominant emission $43.4^\circ \pm 2.0^\circ \pm_{\rm v} 5.9^\circ$ above the equatorial plane, where we separate average structure uncertainty ($\pm$) from the impacts of temporal variability and model misspecification ($\pm_{\rm v}$).

        Speaker: Mr Braden J. Marazzo-Nowicki (McGill University Department of Physics)
      • 13:15
        Can Gravitational Lensing Explain the Extreme Mass Inference of GW231123? 10m

        GW231123 is an exceptional binary black hole merger whose unusually large component masses challenge standard expectations for stellar origins. Additionally, its secondary mass (the less massive one) is in tension with the observed gravitational-wave population. Strong gravitational lensing provides a potential explanation, as magnification biases the inferred source parameters, making a high-redshift, lower-mass system appear much closer and more massive.

        In this talk, I will present the results of an investigation into whether or not gravitational lensing can plausibly account for the observed properties of GW231123. We find that reconciling its secondary mass with the observed population would require an extreme magnification. The probability of observing such a magnification is extremely low given current gravitational wave observations, strongly disfavoring the lensing hypothesis. This work reflects Canada's growing role in gravitational-wave astrophysics, contributing to the global effort to understand the origins of black holes and the reliability of parameter inference, a field in which Canadian institutions are increasingly shaping the scientific conversation.

        Speaker: Mariah Zeroug (CITA, University of Toronto, Dunlap Institute)
      • 13:25
        A Synchronisation Gate for Adapting MKID Photon-Counting Data to Fourier-Transform Spectral Reduction 10m

        Imaging Fourier-transform spectrographs (IFTS) such as SITELLE record spectral information by scanning a Michelson interferometer mirror and are reduced with the ORBS pipeline, which assumes conventional camera-style, frame-based exposures. We are developing a laboratory prototype IFTS built around Microwave Kinetic Inductance Detectors (MKIDs): energy-resolving, photon-counting sensors that read out continuously rather than in discrete frames. This mismatch between MKID's continuous photon stream and ORBS's frame-based input format is the central obstacle to reusing existing SITELLE-heritage reduction software for the new instrument.

        We present the Synchronisation Gate, a software module that reconciles the two data formats by binning the continuous MKID photon stream along two axes simultaneously: mirror position, using timestamps from the interferometer's actuator log to isolate stable-alignment windows, and photon energy, using each photon's intrinsic energy resolution. An efficient binary-search-based algorithm converts the raw photon table into a (step, energy bin, y, x) frame array that ORBS can ingest directly. Because MKIDs resolve photon energy natively, this also enables an "N-cube" strategy: splitting one photon stream into N independent energy-sliced datacubes, each reduced in parallel through a modified ORBS roadmap that bypasses SITELLE's two-camera-specific calibration steps.

        The gate has been implemented and integrated into the lab's MKID data pipeline and validated against synthetic photon-stream data. Remaining work includes full end-to-end validation on real detector data and flux calibration without on-sky standards. This work demonstrates a practical path for extending mature astronomical spectral-reduction software to a fundamentally different detector technology.

        Speaker: Irmak Aytekin (University of Toronto)
      • 13:35
        In-band spectral index techniques for extended radio sources 10m

        Spectral indices are an effective technique for differentiating between thermal and non-thermal sources of radio emission. Most often, spectral indices are determined using flux measurements taken from multiple observations with different instruments. Since this data is not always available, finding indices from a single telescope observation is desirable. The reliability of these in-band spectral indices has not been well studied, particularly for extended sources. I will discuss three different techniques for finding in-band spectral indices using EMU (Evolutionary Map of the Universe) data from ASKAP (the Australian Square Kilometre Array Pathfinder). These techniques include: integrating fluxes in sub-bands, temperature-temperature plots, and utilizing the Taylor terms produced in the imaging process. I apply these techniques to a selection of extended sources of radio emission, primarily supernova remnants (SNRs) and HII regions, and assess if the indices produced by the different techniques agree with the expected values. I examine how well the in-band techniques can differentiate between the thermal (HII regions) and non-thermal (SNRs) source.

        Speaker: Brianna Ball (University of Alberta)
      • 13:45
        An Exposure Time Calculator for CASTOR's UV Multi-Object Spectrograph 10m

        The Cosmological Advanced Survey Telescope for Optical and UV Research (CASTOR) is a proposed 1 meter space telescope under development by the National Research Council of Canada, the Canadian Space Agency, and partner institutions around the world. It will serve as a successor to the Hubble Space Telescope (HST) at short wavelengths, providing continued access to the ultra-violet (UV) and blue-optical at high spatial resolution (~0.15”) over a field of view ~100x larger than HST. The UV Multi-Object Spectrograph (UVMOS) is a medium resolution (R~1500) spectrograph based on the BATMAN spectrometer that is proposed as a parallel instrument onboard CASTOR. A UVMOS has been identified as one of the possible Canadian contributions towards NASA’s Habitable Worlds Observatory. Here we present a pixel-based, user-friendly, extensible exposure time calculator (ETC) for the CASTOR UVMOS instrument, adaptable for other space-borne MOS missions, as well as illustrative science cases outlining the unique capabilities offered by CASTOR UVMOS in the next decade.

        Speaker: Ms Jade Yeung (University of Manitoba)
      • 13:55
        Model Predictive Scoring shows specific BAO points (not Supernovae) drive the dynamic dark energy tension 10m

        The recent analyses of DESI DR2 BAO, Planck CMB and various Supernovae datasets have shown preferences for dynamic dark energy (DDE) over cosmological constant at various levels of significance, under frequentist model comparison tests. However, the same analysis done with a pure Bayesian model comparison test can lead to the opposite conclusions. In contrast to these traditional model comparison metrics, we approach the problem along a third axis -- which model better predicts unseen data. We use the Expected Log Predictive Density (ELPD) metric to score the predictiveness of cosmological constant and DDE models, using the leave-one-redshift-block-out cross-validation estimator. Aggregated, we find modest preferences for DDE, primarily driven by the BAO. Decomposing the ΔELPD score by redshift we find that a single BAO tracer, LRG2 (z=0.706), supplies the entire DDE preference. Interestingly, the biggest outlier point, LRG1, contributes little to the model predictive scoring because both models fail to predict the observation by equal amount. On the other hand, all SNIa datasets' ΔELPD scores are consistent with 0, indicating that at an out-of-distribution predictive level, the DDE tension is entirely driven by one BAO point, not SNIa.

        Speaker: Tanveer Karim (University of Toronto)
      • 14:05
        Tangled $τ$ and Flash Reionization 10m

        Recent cosmological tensions have renewed interest in the role of reionization in cosmological parameter inference. In particular, “flash reionization” has been proposed as a transient episode of ionization at high redshift that could increase the Thomson optical depth, $\tau$, while remaining compatible with CMB polarization measurements.

        In this work, we present the first Markov Chain Monte Carlo analysis of flash reionization using Planck CMB temperature, polarization, and lensing data. Using Planck PR4, we find that the CMB permits a wide range of flash redshifts, with the allowed redshift strongly correlated with the peak ionization fraction. For benchmark scenarios at $z_{\rm flash}=20$ and $25$, we obtain $x_{\rm flash}=0.24^{+0.13}_{-0.07}$ and $0.15^{+0.07}_{-0.05}$, respectively.

        Despite this additional freedom in the ionization history, the standard $\Lambda$CDM parameters remain largely unchanged. In particular, we find $\tau = 0.061\pm0.007$
        compared with $\tau=0.059\pm0.006$ for standard tanh reionization. Interestingly, repeating the analysis with Planck PR3 removes the mild preference for a flash and instead yields upper limits on its amplitude. I will discuss what these results tell us about how much non-standard reionization history can be hidden within current CMB data and the implications for cosmological inference.

        Speaker: Param Upadhyay (UManitoba)
    • 12:45 → 14:15
      Exoplanets & Stars: Full contributions
      • 12:45
        Can Super-Earths Be Born Rocky? Separating Survey Selection from Formation in the Deficit of Large Rocky Planets at Low Insolation 10m

        Small planets show a radius valley near 1.8 R⊕ splitting them into rocky super-Earths and volatile sub-Neptunes, but whether rocky planets can be born rocky, or are all stripped cores of planets that lost an envelope, is still unsettled. We test two planet formation scenarios, Sub-Neptune (no planet born rocky) and Sub-Neptune+Super-Earth (some are), as priors to analyze this question. We build the scenarios by building synthetic planet populations, where we tested two independent generators (occurrence-weighted P-Pop and a flat uniform-parameter control). The two scenarios are then pushed through calibrated Kepler, TESS, and HARPS/NIRPS detection pipelines, and compared against the NASA Exoplanet Archive, filtered with precision control ≤25% mass/≤8% radius uncertainty (125 planets after the filter). The analysis in comparison with NASA include a forward Monte Carlo comparison and a Bayesian posterior-predictive test, during which we used a metric based on the detected population's rocky-to-volatile fraction. As for the result, at low insolation (S < 50 I⊕), the 25 NASA cold super-Earths favor Sub-Neptune under every relation and both generators (√x = 2.10 vs 6.25 in the Bayesian test). An important thing to note is that absolute completeness of detection in this cold regime is only ~1%, driven almost entirely by the ~2% geometric transit probability of long orbits, rather than photometric sensitivity, so the raw scarcity of cold rocky planets alone says nothing until assessed in detected space. We also finds that the result fails when the uncertainty control is relaxed from ≤25% mass/≤8% radius to ≤30% mass/≤10%, and only 4 of 25 cold super-Earths are rocky at high confidence. In conclusion, we read the result as most rocky super-Earths coming from atmospheric escape rather than being born rocky. We believe that identifing more precise cold-planet masses, concentrated among K/M dwarfs, where detection efficiency stays near 50%, are needed to settle it.

        Speaker: HongYi Mei (University of Toronto)
      • 12:55
        Oxygen abundances as a key predictor of small planet hosts using gradient boosted decision trees 10m

        Using a novel crossmatch of GALAH DR4 stellar abundances with K2 and TESS planet detections, we apply the gradient boosted decision tree ensemble model XGBoost to investigate relative importances of specific chemical abundances and molar ratios in predicting small planet hosts. In contrast to previous studies, we find a consistently high feature importance for oxygen across models. Using a probability threshold of P > 0.80, the [X/O] ensemble identifies 1,218 likely small-planet hosts, including 13 of 133 K2/TESS candidates. Abundance distributions reveal that the observed signal may be driven primarily by oxygen depletion. These results provide a targeted shortlist for follow-up observations while highlighting the need for larger host samples and more granular comparisons between planetary subclasses.

        Speaker: Rosalind Liang (University of Victoria)
      • 13:05
        Determining Stellar Inclinations and True Planet Mass with RVs 10m

        I aim to determine the inclination of the rotation axis of stars that host exoplanets and to use that information to find the true mass of their exoplanets. To detect exoplanets via the radial velocity method, one measures the minute redshifts and blueshifts in a star’s spectrum as a star’s planet causes orbital reflex motion towards and away from the observer. The strength of the radial velocity signal depends on the planet’s mass and its a priori unknown orbital inclination–the rotational plane tilt relative to the observer. Without knowing the inclination, the radial velocity technique can only provide a lower limit on the planet mass–a limitation for the past 30 years. If one can find the stellar rotation axis inclination and assumes that the planet’s orbital inclination is perpendicular to the stellar rotation axis, one can find the planet’s true mass. My research investigates a new method of determining the stellar rotation axis from RV observations by analyzing and modeling the changes in both stellar radial velocity and surface temperature shifts as a function of time. I use data from the NIR spectrographs NIRPS and SPIRou and reduce it via the line-by-line technique (LBL) to measure both the stellar RV and temperature variations (dTemp), modeling the outputs with starry and fitting the stellar rotation axis inclination with MCMC sampling, from which a true planet mass can be found.

        Speaker: Riley Rosener (Université de Montréal)
      • 13:15
        GAUCHO: Searching for Planets Around the Coolest Stars in the Galaxy 10m

        Ultra-cool dwarfs are the smallest and coolest stars on the main sequence. While M dwarfs are generally known to harbour a large number of planets, including rocky, Earth-mass exoplanets, the occurrence rate and architectures of planetary systems around ultra-cool dwarfs remain poorly constrained. To date, the only well-characterized planetary system around an ultra-cool dwarf is the TRAPPIST-1 system. This regime is the last to be constrained by radial-velocity studies. The Grasping exoplanet Architectures of Ultra-Cool HOsts (GAUCHO) project is a blind radial velocity survey of about 15 ultra-cool dwarfs with the NIRPS high-resolution spectrograph. In the long term, GAUCHO aims to constrain the occurrence rate of systems like TRAPPIST-1 and super-Earths around ultra-cool dwarfs, map typical long-orbit architectures (>10 days) of ultra-cool dwarf systems, and measure their fraction of brown-dwarf companions. Here, we give an overview of the GAUCHO target sample and present preliminary results focusing on target selection for prolonged observations within the NIRPS GTO program. These results highlight the significant challenges associated with blind radial velocity searches of faint targets.

        Speaker: Flavie Bélanger (UdeM/IREx)
      • 13:25
        Freckled and Flaring: Statistical Starspot Mapping on M Dwarfs via Stellar Flares 10m

        The spatial distribution of starspots on red dwarf stars remains an open question in stellar astrophysics. Understanding whether red dwarfs’ starspots are preferentially equatorial—akin to the Sun—or are preferentially polar can give us insight into how these generate their magnetic dynamos and help to better characterize the atmospheres of the planets that orbit them as atmospheric observations are heavily contaminated by starspots. Most tested surface mapping techniques are either observationally expensive or highly degenerate, making it difficult to obtain a population-level understanding of starspot distributions. Fortunately, stellar flares, which result from magnetic reconnection events that are spatially correlated with starspot locations on the Sun, make flare observations a powerful diagnostic of starspots on distant stars. I have developed and rigorously tested a framework to detect stellar rotation and energetic flares in light curves from NASA’s Transiting Exoplanet Survey Satellite, which I am using to correlate flare times with stellar rotational phase as a proxy for the distribution of starspots. My early analysis of over 6,500 red dwarfs suggests that, regardless of the interior stellar dynamo, these stars are dominated by equatorial starspots.

        Speaker: Rohan Kumar
      • 13:35
        EncoTESS: Age Inference from Raw TESS Light Curves 10m

        Stellar ages are a foundational component of astronomy research, but are notoriously difficult to measure for low mass main sequence stars. Fortunately, variability indicators such as rotation period, flaring rate, and amplitude of flux variability can provide some age constraints, but they evolve in nonlinear and non-monotonic ways. Furthermore, these indicators are typically characterized as summary statistics from time series data, but these are often noisy, treated independently, and do not capture all of the useful information contained in raw light curves. With the recent advances in ML/AI and computing combined with the vast number of light curves available from Kepler and TESS, there is a prime opportunity to apply more data-driven methods. To that end, I have developed and here present \texttt{EncoTESS}: a Time Series Foundation Model that can be used to estimate stellar ages from raw TESS light curves without using summary statistics. I show that through self-supervised training, \texttt{EncoTESS} naturally captures stellar variability, and that it can be used to infer the ages of young M dwarfs with more accuracy and precision than rotation-based models. \texttt{EncoTESS} is designed with consideration of crucial systematics such as noisy, heteroskedastic data with large gaps, and implements an architecture expandable to multi-cadence and multi-survey light curves for broader applicability in the future. It is also ~1% of the size of typical literature Time Series Foundation Models, and can be run easily on any modern laptop.

        Speaker: Phil Van-Lane (University of Toronto; University of California San Diego)
      • 13:45
        Exploring Convective Boundary Mixing Through Stellar Pulsations 10m

        Convective boundary mixing occurs at the boundaries between convection and radiation zones in stars, where the material in the convection zone crosses the convective boundary. This can change the location of the convective boundary and bring more hydrogen into the core of the star, which has many effects on its evolution, including an extended main sequence lifetime. We use 1D stellar evolution code MESA (Modules for Experiments in Stellar Astrophysics) to make models of stars with various convective boundary mixing processes, and calculate pulsation frequencies for the models with the GYRE stellar oscillation code. We then use the pulsation frequencies of the models to compare the effects of these different processes, and their implementations in MESA, on the star. Our goal is to find some difference caused by the different convective boundary mixing processes that could potentially be observed in real stars. This will help us understand how these processes occur in stars, enabling more accurate predictions of stellar evolution.

        Speaker: Serena Davis (Mount Allison University)
      • 13:55
        Developing a Recurrent U-Net for Faint Trans-Neptunian Object Detection Using Synthetic Injections 10m

        Trans-Neptunian Objects (TNOs) are small, distant bodies beyond Neptune that provide important context on the formation and evolution of the outer Solar System. However, the faintest TNOs are difficult to detect because their weak signals can be easily confused with noise and subtraction artifacts. Manual identification of genuine TNOs is therefore a time-consuming process that can require hours of careful inspection. To automate the process, this project develops a recurrent U-Net framework for identifying faint moving sources, with particular emphasis on generating realistic and well-characterized training data. A synthetic injection pipeline, maketensor, was developed to implant artificial TNOs directly into real difference-image observations. Each source is propagated across multiple exposures with physically motivated apparent motion and injected using the point-spread function corresponding to each observation. The underlying noise, stellar residuals, detector features, and other observational artifacts are preserved to keep the training data authentic. The pipeline also reproduces characteristic subtraction effects and negative wells, allowing the synthetic objects to more closely resemble real TNO signatures. The resulting multi-frame tensors contain real observational backgrounds with exact ground-truth locations and trajectories for every injected source. These sequences are used to train a recurrent U-Net to produce pixel-wise probability maps that identify likely TNO locations across a sequence of exposures. By learning the consistent motion of a TNO across successive frames, the network aims to distinguish genuine moving sources from noise and image-subtraction residuals, enabling faster and more reliable detection of faint TNOs in large astronomical datasets.

        Speaker: Ms Malavika Nair (Western University)
    • 12:45 → 14:15
      Galaxies, Gas/dust, Solar system & Stars: Full contributions
      • 12:45
        WEAVE-Pristine survey: NLTE-Informed Machine Learning for Stellar Parameters and Abundances in Pristine-selected metal-poor stars. 10m

        Homogeneously analysing the chemical signatures of the Milky Way’s most pristine metal-poor stars is essential to reconstruct its early assembly and first-star nucleosynthetic yields. Over the next few years, WEAVE in the North and 4MOST in the South will enable high-resolution, multi-object spectroscopic follow-up of millions of Gaia stars. We present a machine learning pipeline for the WEAVE-Pristine survey to automate analysis of high-resolution (R ~ 20,000) spectra of very ([Fe/H] < -2) to extremely ([Fe/H] < -3) metal-poor star candidates in the Pristine Data Release 2. The neural network is trained on +100,000 synthetic spectra interpolated from the MARCS atmosphere grid and varying 15 elements of which 9 of them were computed in Non-Local Thermal Equilibrium (NLTE) using the MPIA/1DNLTE spectral synthesis code. To reduce the synthetic gap, we augment the spectra on-the-fly during training with WEAVE instrumental effects. Thus, we have an end-to-end pipeline that spans from the generation of raw synthetic spectra to the final prediction of stellar labels and their uncertainties, including atmospheric parameters (Teff, log g, [Fe/H], microturbulence) and individual chemical abundances [X/Fe] for 15 species: alpha-elements (O, Mg, Si, Ca, Ti), iron-peak (Cr, Mn, Ni), light elements (Na, Al), neutron-capture (Sr, Ba, Eu), and C/N. The pipeline is tested on both synthetic and observed spectra from early internal release of WEAVE observations, including stars in the very metal poor globular cluster M15 and the solar metallicity open cluster NGC 6819.

        Speaker: Minjih Kim (University of Victoria)
      • 12:55
        Unlocking the evolution of star formation with CASTOR 10m

        Ultraviolet observations provide a direct view of young stellar populations associated with recent star formation in galaxies, complementing longer-wavelength observations that trace older stellar populations. The Canadian-led Cosmological Advanced Survey Telescope for Optical and ultraviolet Research (CASTOR) will provide wide-field coverage with deep imaging fields, enabling large samples of low-mass galaxies to be studied through recent star formation. We investigate how addition of CASTOR observations affects recovery of galaxy star formation rates (SFRs) from photometric spectral energy distribution (SED) fitting. We construct forward-modelled galaxy spectra using Binary Population and Spectral Synthesis models and galaxy populations drawn from Santa Cruz semi-analytic model lightcones at 0<z<5. Mock CASTOR, Euclid, and SDSS observations are generated to provide panchromatic coverage from the ultraviolet to the near-infrared, and SFR recovery is assessed using SED fitting with and without CASTOR observations. We find an improvement in SFR recovery accuracy from 0.54 to 0.28 dex at z<1 when incorporating CASTOR observations, while over 0<z<5 the difference decreases from 0.34 to 0.28 dex. CASTOR also increases the number of galaxies meeting our SED-fitting detection criteria by 61 percent, with approximately three-quarters of the additional galaxies undetected in Euclid and SDSS bands. These additional galaxies are predominantly among the lower-mass and lower-SFR systems in the sample. Our results demonstrate that deep ultraviolet observations provide important complementary constraints on photometric SFR estimates, particularly at low redshift, while also enabling large samples of faint, low-mass galaxies to be studied alongside longer-wavelength observations.

        Speaker: Dr Gareth Jones (University of Manitoba)
      • 13:05
        Searching for Carbon-Enhanced Metal-Poor Stars in DESI 10m

        Carbon-enhanced metal-poor (CEMP) stars are some of the oldest and most chemically primitive stars in the Milky Way. They are defined by excess carbon and low metallicity, and further classified by neutron-capture enrichment. The origin of this unique enrichment varies between CEMP subclasses. Neutron-capture-enriched CEMP stars reflect previous extrinsic enrichment events, whereas CEMP stars with no neutron-capture enrichment (CEMP-no) are believed to be intrinsically enriched, reflecting progenitor conditions. These varying enrichment histories provide key insights into nucleosynthetic processes and the nature of the first stars. A challenge that remains for their study is the lack of large-scale, homogeneous data. The scale problem may be addressed through major stellar surveys such as the Dark Energy Spectroscopic Instrument (DESI) Milky Way Survey Program. While DESI observes deeper into the Galactic halo and at lower magnitudes than other stellar surveys, its resolution and signal-to-noise ratio make it difficult to classify CEMP stars using provided chemical abundances. Using DESI DR1 spectra, we constructed a method for flagging stars as CEMP using the CH-G band and the strontium line at 4077Å. This rough scheme separates CEMP-no stars from remaining CEMP subclasses. It correctly classifies ≥80% of stars in common between DESI and high-resolution literature samples, and ≥95% of stars in common between DESI and other surveys. We found a total of 3,154 CEMP stars with a metallicity as low as -4.0 dex. High-resolution follow-up will be performed on the most viable candidates.

        Speaker: Ms Rosayla Coulthard (University of Toronto)
      • 13:15
        Identifying Candidates of Partially Stripped Yellow Supergiants 10m

        Despite the traditional model of a Yellow Supergiant as a brief transitional phase in a star’s life before the onset of core helium burning, there is an increasing catalog of supernovae explosions that have had their progenitors identified as Yellow Supergiants from pre-explosion imaging. Notably, these supernovae are both partially-stripped and hydrogen-poor. The widespread interpretation for these observations is that a binary companion partially strips the supernova progenitor of its stellar envelope, after which it subsequently explodes as a Yellow Supergiant, having the appropriate temperatures and luminosities for this regime. Still, no analogs to these partially-stripped Yellow Supergiants have been discovered in Local Group galaxies that can be studied in detail prior to their explosion. Theoretical models predict that certain pulsations should be excited exclusively in partially stripped Yellow Supergiants, resulting in unique lightcurve morphology. Therefore, the variability of Yellow Supergiants can provide unique insight into their stellar structure and the presence of a full or partially-stripped hydrogen envelope. I will describe the ongoing program to characterize the variability of hundreds of YSGs in the Magellanic Clouds with the goal of finding potential partially-stripped Yellow Supergiants. In particular, I will highlight the identification of candidate Yellow Supergiants to date that have the predicted hallmarks of partially stripping, and describe on-going follow-up efforts to confirm the nature of this sub-population.

        Speaker: Shannon Bowes (University of Toronto)
      • 13:25
        Bridging the gap between Milky Way and extragalactic star formation studies 10m

        Measurements of massive star formation from Galactic and extragalactic cloud-scale observations produce conflicting results. Theory predicts that gas surface density, velocity dispersion, virial parameter, and gravitational freefall time should play a key role in setting the timescale for star formation. Milky Way observations support this prediction. In extragalactic systems, observations find weak, or even anti-correlations, with predictions from theory. There remains, however, a significant gap between the scales probed in extragalactic surveys (50-150pc) and the resolved cloud observations from Milky Way studies (~10pc) which could account for this tension. This work addresses the spatial gap between these studies using new ALMA 12CO(2–1) and 12CO(1-0) observations of M33. The resolution of these data (~10pc) matches the spatial scales resolved in Milky Way studies allowing for direct comparisons to be made. We measure star formation rates using the early embedded phase of massive star formation, enabled by JWST observations. Using these data, we find no strong correlation between the star formation efficiency and molecular gas properties in resolved extragalactic molecular clouds. Our results find that the tension between Milky Way and extragalactic observations cannot be attributed to a gap in spatial scales. Future work will extend our study of resolved cloud observations to local volume galaxies across a range of galactic environments.

        Speaker: Hannah Christie (University of Alberta)
      • 13:35
        Leveraging CANFAR and the ALMA archive to create SALVAGE - II: the effect of AGN feedback on central molecular gas 10m

        Understanding the mechanisms that drive and halt star formation requires an assessment of both the stellar and gaseous components of a large statistical sampling of galaxies. For Canadian astronomers, large optical surveys have adequately serviced the stellar components, but large samples of resolved molecular gas observations are challenging to acquire. However after 13+ years of operations, the ALMA Science Archive has accumulated an untapped wealth of molecular gas observations waiting to be analyzed as an ensemble. Enabled by the CANFAR Science Platform, the SDSS-ALMA Legacy-Value Archival Gas Exploration (SALVAGE) dataset encompasses ~300 galaxies with optical data from the Sloan Digital Sky Survey (SDSS) and CO(1-0) maps from ALMA. Together, these products allow for a “semi-resolved” perspective of the gas and stars, meaning that the inner ~2kpc (set by the SDSS spectroscopic fibre diameter) and outer regions can be independently studied.

        In this presentation, I will use SALVAGE to quantify how feedback from an active galactic nucleus (AGN) affects the molecular gas. Although simulations show that AGN feedback can remove gas from galaxies, nearly all observational studies of low-redshift AGN show no evidence of gas depletion. Recent works have found that AGN can only remove gas from the central regions, but are limited to small samples. SALVAGE allows us to test this result with substantially larger statistics. Using a sample of 70 AGN and matched non-AGN controls, I will assess whether AGN hosts show evidence for reduced central molecular gas, providing observational constraints on the role of AGN in galaxy evolution.

        Speaker: Scott Wilkinson (Queen's University)
      • 13:45
        Visibility Plane Forward Modeling of Young Massive Clusters within the Nuclear Ring of NGC 3351 10m

        Using high-resolution ALMA millimeter observations, we investigate the formation of massive star clusters within the nuclear ring in NGC 3351, a nearby Milky Way analog galaxy. The dense, high-pressure conditions within nuclear rings are among the most extreme star-forming settings in the local universe, providing the ideal conditions for massive cluster formation. Nevertheless, the mechanisms driving massive cluster formation and the impact of environmental conditions remain poorly understood. They are distinct from lower-mass clusters in that they form quickly and convert gas to stars efficiently, doing so before the significant onset of stellar feedback from newly formed stars. To study the full conditions of massive cluster formation, we must observe their short, infant stages when they are actively star-forming and newborn stars remain deeply embedded in gas and dust. This phase is best traced by (sub-)millimeter observations. We perform our analysis directly in the raw visibility plane using the GALARIO package to convert forward models of the region into model visibilities sampled at the same baselines as our observations. This approach avoids image-plane-based reconstruction methods that produce artifacts and correlated noise, and it preserves the full data resolution, allowing us to better constrain the intrinsic radial profiles of the young massive clusters and the physics of their star formation. Furthermore, we can derive higher-fidelity estimates and uncertainties of the shared morphology of the ring and clusters, contributing to our understanding of how gas accretion onto the nuclear ring drives massive cluster formation along its structure.

        Speaker: Peter Knowlton (University of Victoria)
      • 13:55
        Bridging the Gap in the New Era of Star Formation 10m

        With the advent of JWST imaging in the Local Group, young stellar objects (YSOs) are being observed in a broader range of environments than ever before, which will revolutionize our understanding of star formation if their properties can be modelled accurately. We present a new approach to characterizing YSO populations by applying the technique of population synthesis originally developed for older stellar populations (Peltonen et al. 2026). Using the latest YSO radiation transfer and stellar evolution models, we have developed a population synthesis code that can generate YSO populations, accounting for details like binaries, clustering, extinction, and stochastic sampling. We used this new code to determine the properties of YSOs in the recent JWST images of NGC 604 within M33 and previous Spitzer studies of the LMC. This approach allows us to measure the star formation rate in extragalactic systems directly from YSOs instead of relying on tracers from massive stars (Halpha, photospheric emission). With this powerful technique, we can also turn to local clouds in the Spitzer Extended Solar Neighborhood Archive (SESNA). We present preliminary results to constrain the star formation histories in the SESNA molecular clouds. Ultimately, this population synthesis framework will allow us to evaluate the current star formation properties in any region with an observed YSO population and allow us to directly connect the Milky Way star formation properties to those of extragalactic systems.

        Speaker: Mrs Jaiden Peltonen (University of Alberta)
      • 14:05
        Search for 21-cm absorption systems with CHIME 10m

        Neutral atomic hydrogen is the primary raw material from which stars form in galaxies; and understanding its spatial distribution, kinematics, and thermal state across cosmic time is therefore fundamental to our comprehension of how galaxies assemble and evolve. The 21-cm hyperfine transition of neutral hydrogen is a powerful probe of cold gas in and around galaxies across cosmic time. When a radio source lies behind a cloud of neutral hydrogen, the cold gas imprints a characteristic absorption feature in the spectrum of the background source at the redshifted 21-cm frequency. Unlike 21-cm emission, the absorption feature is detectable independently of the distance to the absorber, so its detectability does not diminish with redshift. Despite this advantage, the known sample of extragalactic 21-cm absorbers at redshifts z > 1 has remained small: only 42 systems were known prior to this work, reflecting the scarcity of suitable radio facilities at the relevant frequencies.

        In this talk, I present the results of a pilot blind search for 21-cm absorption systems conducted with the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a radio telescope operating between 400 and 800 MHz, which corresponds to the 21-cm line at redshifts 0.78 < z < 2.55. This pilot survey resulted in the discovery of a new 21-cm absorber at z = 2.327, which is only the fifth known absorber associated with a quasar at z > 2. The survey also recovered two previously known intervening absorbers, validating the detection pipeline.

        Speaker: Arash Mirhosseini (Dunlap Institute for Astronomy & Astrophysics, University of Toronto)
    • 12:45 → 14:15
      Galaxies: Full contributions
      • 12:45
        Measuring Simulated Circumgalactic Medium Turbulence with Emission-Weighted Projected Velocity Structure Functions in FOGGIE 10m

        The spatially-resolved kinematics of line emission from the circumgalactic medium (CGM) of a galaxy can contain information about the CGM turbulence, which may play an important role in galaxy evolution. Due to the region's diffuse nature, there have been limited observations of low-redshift CGM emission until recent efforts that use spatially-resolved emission line kinematics to probe CGM turbulence. We use velocity structure functions (VSFs) as a measure for the properties of turbulence using the high-resolution cosmological zoom-in FOGGIE simulations. We focus on the location of the "turnover" in the VSF slope, often used as a measurement of the turbulence driving scale, and study how resolution, measurement area size, projection effects, and gas temperature influence the inferred CGM turbulence driving scale. We find that projection significantly lowers the VSF normalization but we do not find significant differences in the slope between 3D VSFs and emission-weighted projected 2D VSFs. We find that the size of the area used to measure the VSF, which can be thought of as the size of the emission nebula for a given instrument sensitivity, correlates directly with the turnover location in the VSF. These dependencies should be considered when using VSFs to interpret CGM turbulence from emission data, as projection, resolution and sensitivity constraints, and the temperature of the gas probed will all have a measurable effect on the VSF structure and the corresponding inferred turbulent properties.

        Speaker: Helena Bouchereau
      • 12:55
        A Systematic Census of Strongly Lensed Population III Galaxy Candidates at z ~ 6–7 from JWST VENUS and MUSE 10m

        The first generation of stars, Population III (Pop III), likely played a fundamental role in the formation and evolution of early galaxies. Recent JWST observations have opened a new window for systematically identifying Pop III signatures at high redshift (z ≈ 3–6), during the universe’s first few billion years, including strong hydrogen emission and weak or absent metal lines such as [O III], and have revealed a small but growing candidate sample. We conduct a systematic search for extremely metal-poor, Pop III–like galaxies at z ∼ 6–7 using JWST/NIRCam imaging from the VENUS survey, the largest lensing-cluster program to date. Combining this data with deep MUSE spectroscopy, we search for strongly lensed Pop III candidates whose light is magnified by foreground galaxy clusters. Our search yields two candidates with spectroscopic redshifts that satisfy our selection criteria, including a highly magnified (μ ∼ 28), otherwise inaccessible, intrinsically ultra-faint galaxy (M_UV = −15.3) at z = 5.72. This source exhibits strong, spatially extended Lyα emission, an extreme Hα equivalent width (∼2920 Å), a prominent Balmer jump, and no detectable [O III] in current data—textbook signatures of a young, metal-poor stellar population consistent with Pop III–like systems. MUSE observations reveal multiple Lyα emitters at the same redshift in the field, suggesting that the local environment may help sustain such systems even at z = 5.7. We present the source-plane properties of these candidates, their environments, and constraints on the number density of Pop III–like galaxies at z ∼ 6–7.

        Speaker: Gavin Farley (University of Toronto)
      • 13:05
        Galaxies in JWST’s mirror may be more massive than they appear: bottom-heavy initial mass functions at z ~ 0.7 from JWST-IMFERNO 10m

        JWST's discovery of extremely massive, quiescent galaxies in the early Universe has introduced significant tension with current galaxy formation models, implying that galaxies formed and quenched faster and earlier than expected.  However, estimates of distant galaxy masses are highly uncertain.  They assume a stellar initial mass function (IMF) similar to that in the Milky Way, despite evidence that the cores of massive, local ellipticals (the likely descendants of these massive, high-redshift galaxies) are richer in low-mass stars (i.e. they have a bottom-heavy IMF).  Until now, it has been impossible to robustly measure the IMF beyond the low-redshift Universe in individual galaxies, as extremely deep spectra covering both optical and near-infrared wavelengths are required.  The JWST-IMFERNO program, which combines deep, optical spectra from the LEGA-C survey with extremely deep, near-infrared, JWST/NIRSpec-MSA spectra, has unlocked this challenging constraint.  I will present the first robust measurements of the IMF beyond the local Universe.  Using a sample of 9 massive, quiescent galaxies at z ~ 0.7, I will demonstrate that distant galaxies have bottom-heavy IMFs compared to the Milky Way, implying higher stellar masses than previously estimated.  Finally, I will discuss how our galaxies, which are direct descendants of JWST’s “impossibly early” galaxies, amplify tensions with galaxy formation models.

        Speaker: Chloe Cheng (University of Toronto)
      • 13:15
        The Influence of Bars on Gas Concentrations and Star Formation in Nearby Galaxies 10m

        Galactic bars exist in over half of the galaxies in our local universe, but studies of the resolved gas properties in the bar have been limited to small samples of star forming spiral galaxies. The ALMA program Kiloparsec Investigations of Local Objects’ Gas And Star-formation (KILOGAS) is a survey of the molecular gas in 450 mass-selected galaxies covering the full parameter space of star forming, quenching, and quiescent galaxies. At redshifts between 0.015 and 0.06, all galaxies have unprecedented spatial resolution of 1 kpc that are matched with optical field spectroscopy from the MaNGA and SAMI surveys, allowing for a detailed comparison of the molecular gas with resolved properties from ionized gas such as stellar mass, star formation rates, and metallicity. I will present results of our analysis using radial profiles of molecular gas surface density and star formation rate surface density, where we have found that galaxies with a strong bar have more centrally concentrated molecular gas and star formation. Our findings are broadly consistent with results from Chown et al. (2019) who used a smaller sample of star forming galaxies and found that galaxies with higher molecular gas concentrations and centrally enhanced star formation tend to be barred galaxies. We expect gas concentrations to be higher due to gas inflows along the bar which have been found to suppress star formation efficiency. I will further present results from a full classification of barred galaxies in the KILOGAS sample using both optical and position-velocity diagrams.

        Speaker: Jennifer Laing (McMaster University)
      • 13:25
        How Environment Shapes Quiescent Galaxy Stellar Halo Assembly: Insights from Extended Light and Color Profiles 10m

        Galaxies do not grow in isolation. Interactions with neighboring galaxies and material in their surrounding cosmic environments can drive stellar mass assembly and morphological evolution. Galaxy stellar haloes retain signatures of these externally driven processes due to the long dynamical timescales in galaxy outskirts. Observations tracing stellar halo buildup therefore provide a probe of how merger-driven accretion and environmental processing shape galaxy assembly over cosmic time. In this talk, I will present a combined investigation of stellar halo evolution in quiescent galaxies (QGs) across cluster and field environments over 0.1 ≤ z ≤ 1.0. Using deep CLAUDS+HSC-SSP multiband imaging, we measure rest-frame g-band light and (U−g) color profiles extending to 10Rₑ for ∼90,000 QGs with log(M★/M☉) ≥ 9.66. We isolate environmental effects by comparing the evolution in median light and color profiles of cluster QGs with those of stellar mass- and redshift-matched field QGs, tracing both the buildup of stellar halo material and the evolution of extended radial color gradients. Our results indicate that high-mass cluster QGs exhibit enhanced stellar halo growth fueled by increased accretion. This accretion likely arises from minor mergers occurring in cluster outskirts or pre-infall groups, which deposit bluer stellar populations (younger and/or lower metallicity stars) into the outskirts of higher-mass cluster QGs. In contrast, low-mass cluster QGs show suppressed stellar halo growth and increased reddening of their outskirts relative to the field. These lower-mass QGs likely lose outer stellar halo material through environmental stripping or accretion by high-mass galaxies during mergers.

        Speaker: Devin Williams (Saint Mary's University)
      • 13:35
        Beyond Diagnostic Diagrams: Spectral Decomposition of Ionizing Sources in MaNGA 10m

        Star formation rates (SFR) and gas-phase metallicities in galaxies are usually measured from strong nebular emission lines under the assumption that young massive stars are the only source ionizing the gas. In galaxies hosting an active galactic nucleus (AGN), or containing old stellar populations, harder radiation also produces these lines, so the standard approach is to classify each region with emission-line diagnostic diagrams and discard anything not purely star-forming. In the MaNGA integral field spectroscopy survey, more than half of the spatially resolved spectra (spaxels) passing our quality cuts fall outside the star-forming region. We apply a deep convolutional neural network that decomposes the full spectrum of each spaxel into a star-forming and a non-star-forming component, for roughly 740,000 spaxels across 6,500 galaxies, and fit each decomposed component for both emission lines and continuum.

        The decomposition can be used in two complementary ways. In star-forming regions, it acts as a correction by removing any residual non-star-forming contamination. We use this technique to reconstruct key galaxy scaling relations and find that the corrections are small. In composite and AGN-dominated regions, it isolates any underlying star formation. We confirm that H$\alpha$-based SFR is substantially overestimated in AGN-classified spaxels, and find that metallicity corrections depend on the type of ionizing source. We demonstrate that this decomposition can be used to extend classical calibrations to regions that are usually discarded in population-level studies, and to further our understanding of how AGN activity connects to star formation and chemical enrichment in galaxies.

        Speaker: Aayushmathi Ashok (University of Victoria)
      • 13:45
        VLA 3 GHz Radio Continuum Mapping of Nearby PHANGS Galaxies: Tracing the Life Cycle of Star Formation 10m

        Massive stars strongly reshape their surroundings through radiation, stellar winds, and eventually supernova explosions, but when these different feedback mechanisms begin to dominate remains uncertain. We present VLA 3 GHz radio continuum observations of 13 nearby PHANGS galaxies to trace the evolution of star-forming regions during their first ~10 Myr. Combining these data with HST, JWST, VLT/MUSE, and AstroSat observations, we separate the radio emission into thermal free–free and non-thermal synchrotron components and connect their evolution to stellar age and other tracers of recent star formation. The radio observations also reveal a small population of 36 embedded, PAH- and dust-continuum-bright but optically faint star-forming regions, representing less than 10% of the radio sources and demonstrating the ability of radio emission to probe the earliest obscured phases of star formation. We find a clear evolution in radio properties with stellar age: from 1–3 to 6–10 Myr, the median thermal fraction decreases from ~61% to ~33%, while the median radio spectral index steepens from −0.05 to −0.51. The youngest regions already exhibit a non-thermal fraction of ~28% before the expected onset of core-collapse supernovae, suggesting that massive-star winds and associated shocks may contribute to early cosmic-ray acceleration. These results provide a resolved view of how radio emission evolves from the embedded phase through the emergence of synchrotron emission during the first ~10 Myr of stellar feedback.

        Speaker: Hamid Hassani (University of Alberta)
      • 13:55
        Finding the boundary: Using galaxy membership to inform galaxy cluster extent through machine learning 10m

        The spatial extent of the environment's impact on galaxies marks a transitional region between cluster and field galaxies. We present a data‐driven method to identify this region in galaxy clusters with masses $M_{200\rm ,mean}>10^{13} {\rm M}_{\odot}$ at $z = 0$. Using resolved galaxy samples from the largest simulation volume of IllustrisTNG (TNG300-1), we examine how galaxy properties vary as a function of distance to the closest cluster. We train neural networks to classify galaxies into cluster and field galaxies based on their intrinsic properties. Using this classifier, we present the first quantitative and probabilistic map of the transition region. It is represented as a broad and intrinsically scattered region near cluster outskirts, rather than a sharp physical boundary. This is the physical detection of a mixed population. In order to determine transition regions of different physical processes by training property-specific models, we categorise galaxy properties based on their underlying physics, i.e. gas, stellar, and dynamical. Changes to the dynamical properties dominate the innermost regions of the clusters of all masses. Stellar properties and gas properties, on the other hand, exhibit transitions at similar locations for low mass clusters, yet gas properties have transitions in the outermost regions for high mass clusters. These results have implications for cluster environmental studies in both simulations and observations, particularly in refining the definition of cluster boundaries while considering environmental preprocessing and how galaxies evolve under the effect of the cluster environment.

        Speaker: Christine Hao (University of Toronto)
      • 14:05
        Inferring Spatial Distributions of Dark Matter in Dwarf Galaxies with ML 10m

        The spatial distribution of dark matter can help us understand the formation and evolution of the structures in our universe. However, dark matter is invisible, so we need to infer its distribution from the motions of visible stars. Previous techniques struggle to handle incomplete and biased datasets, such as missing velocity information, and have difficulty incorporating measurement uncertainties. To mitigate these limitations, we develop Neural Likelihood Estimator (NLE), a machine learning framework which models the probability of seeing a given set of visible stars given a set of dark matter parameters. By applying Bayes’ theorem, we can recover the dark matter distribution of the galaxy from visible stars. Our model not only performs well on synthetic galaxies, but it has proven to outperform traditional methods and modern techniques at recovering the distributions of dark matter from real observational data of the dwarf galaxy Draco. The method is also highly effective at handling uncertainty and incomplete and biased data.

        Speaker: Chun On (Andy) Yu (University of Toronto)
    • 12:45 → 14:15
      Transients & Cosmology: Full contributions
      • 12:45
        Off-axis GRBs and Where to Find Them 10m

        Long-duration gamma-ray bursts (GRBs) are the most luminous explosions in the Universe, visible out to cosmological redshifts. Almost every spectroscopically confirmed supernova (SN) associated with a long GRB has been hydrogen and helium poor with broad lines (Ic-bl), indicating a stripped massive star progenitor with fast winds that produced a highly-collimated jet viewed on-axis. A critical prediction of this progenitor model is that there should be a large number of off-axis jets accompanying SNe Ic-bl - however, this has yet to be observationally confirmed. Additionally, if a GRB is observed moderately off-axis, it may result in a spectrally softer X-ray flash (XRFs), detectable with X-ray observatories such as Einstein Probe and SVOM. Radio observations of XRFs and SNe Ic-bl can reveal late rising afterglows as the jet spreads into the field of view, providing one of the best pieces of evidence for the off-axis GRB scenario. Here, I will present recent results following up several candidate off-axis GRBs, including an XRF and a sample of radio loud SNe Ic-bl. Additionally, I will lay the path forward to detecting off-axis GRBs in the era of large transient surveys.

        Speaker: Genevieve Schroeder
      • 12:55
        Probing the Origins of Fast Radio Bursts Through Searches for Multi-wavelength Counterparts 10m

        Fast Radio Bursts (FRBs) are highly energetic, ~millisecond duration bursts of radio emission with extragalactic origins that were discovered nearly 19 years ago. While there is some evidence suggesting FRBs may originate from magnetars, there still remains the question of whether all FRBs are produced by magnetars. One potential method for further understanding FRB progenitors is through cross-matching FRBs with different transients with a known progenitor by searching for positional, redshift, and/or temporal coincidences. In this talk, I will discuss a new pipeline for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) which automatically cross-matches all FRB candidates with gamma-ray bursts (GRBs) detected by the Swift observatory and Fermi telescope, gravitational waves (GWs) detected by the Ligo-Virgo-Kagra (LVK) collaboration, and optical transients reported in the Transient Name Server (TNS). I will also describe the largest campaign to cross-match over 4000 FRBs with all known gamma-ray bursts (GRBs) to determine radio upper limits for GRBs within CHIME’s field of view. Finally, I will discuss the results of FRB-TNS optical transient crossmatching as a direct test to the FRB progenitor model.

        Speaker: Melanie Szpigiel (McGill University)
      • 13:05
        Evidence for the invisible gas around galaxy halos using fast radio bursts from CHIME/FRB 10m

        Most of the baryonic mass in galaxy halos consists of diffuse, magnetized plasma, which is referred to as the circumgalactic medium (CGM). The properties of the CGM remain relatively unconstrained, as the low density of the gas makes it hard to image in most wavelengths of the electromagnetic spectrum. Fast radio bursts (FRBs) are thus incredibly good probes of this plasma, because they undergo dispersion as they propagate through the CGM.

        I used over 1600 FRB DMs from CHIME/FRB's upcoming Baseband Catalog 2, which is the largest catalog of FRBs that have a localization error of $<1'$, to conduct an unprecedented statistical study of nearby galaxy halos. In doing so, I obtained the strongest evidence ($p = 0.0053;\sim 2.6\sigma$) for a DM excess due to the CGM to date, with an amplitude of $119\pm43\,$pc$~$cm$^{-3}$. I also obtained some of the first FRB-based constraints of the baryon distribution of the CGM of Milky Way like galaxies, with tentative evidence ($\sim2.4\sigma$) that galaxy halos in this mass range may be more relaxed than previously thought, almost tracing the underlying dark matter distribution directly. However, more FRBs are needed to further test this. My work demonstrates the power of FRBs to map the invisible diffuse plasma in the Universe and forecasts a $5\sigma$ detection of the CGM with 10000 FRBs, which can then be used to place the best constraints (amongst all probes of hot plasma) on the distribution of baryons in the CGM.

        Speaker: Affan Khadir (McGill University)
      • 13:15
        Constraining the evolution of dynamic environments surrounding actively repeating fast radio bursts 10m

        Fast radio bursts (FRBs) are short-duration (ms), bright (Jy-kJy) bursts of radio emission, generally originating from cosmological distances. Although thousands of FRB events have been published, the progenitor and emission mechanism of FRBs are still not well understood. While most FRBs appear to be one-off events, ~2% of FRBs have been observed to repeat. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope has detected thousands of FRBs, monitoring a large number of repeaters over multi-year baselines with a daily cadence. Radio spectra of FRBs are uniquely able to probe the properties of the plasma in the FRBs' immediate vicinity. CHIME/FRB’s high time resolution (2.56 μs) and broadband, low-frequency coverage make CHIME/FRB ideal for constraining propagation effects and monitoring them over time. Recent works have discovered secular evolution of the magnetized plasma surrounding a few peculiar repeating FRBs, linking them to young stellar remnants of massive stars. Our project builds on this work by measuring changes in the magnetoionic plasma over a timescale of months to years, for a diverse sample of ~50 repeaters observed by CHIME/FRB. By examining changes in the magnetoionic plasma for a larger population of repeaters, we aim to establish boundaries on the potential progenitor or environment for the general population of repeating FRBs.

        Speaker: Nicole Mulyk (McGill University)
      • 13:25
        The CHIME All-Sky Multiday Pulsar Stacking Search (CHAMPSS) 10m

        The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has been an instrumental telescope in shaping our understand of transient sky by detecting the vast majority of known fast radio bursts (FRBs) using its CHIME/FRB backend. The recently launched CHIME All-Sky Multiday Pulsar Stacking Search (CHAMPSS) uses data from this backend to perform a pulsar periodicity search with unprecedented cadence. In the current configuration we are able to observe about 20% daily of the northern sky which allows us to probe very intermittent sources.

        CHAMPSS is not only a pulsar survey with a high cadence, but our daily allow observations allow us a deep search for faint sources by combining hundreds of observations. We do this by performing power spectra stacking. This approach of doing daily searches combined with searches in our combined power spectra stacks has allowed us to find more than 60 pulsars so far. These new pulsars include binary pulsars, intermittent sources and some of the closest pulsars known to date.

        I will explain the unique challenges and opportunities of our survey and outline our survey pipeline, including recent developments that allow us to be more sensitive to binary pulsars.

        I will also highlight some of our most exciting pulsar discoveries that we have made so far.

        Speaker: Lars Kuenkel (McGill University)
      • 13:35
        Evaluating magnetars as the progenitors of fast radio bursts 10m

        Fast radio bursts (FRBs) are micro-to-millisecond-duration radio transients originating from extragalactic distances. While thousands of FRBs have been detected, their origins remain unknown. Many FRB theories invoke highly magnetised neutron stars, called magnetars, as FRB progenitors. In this talk, I will evaluate the magnetar progenitor scenario using recent results from the CHIME/FRB telescope.
        The most energetic FRBs provide crucial insights into their emission mechanisms and progenitor models. I will present constraints on the maximum energy of FRBs derived from the largest sample of ~3,000 one-off bursts in the second CHIME/FRB catalog. Our results indicate that the isotropic energies of the most energetic FRBs are collectively limited to ~$10^{42}$ erg, thereby constraining the energy reservoir of their sources. Under standard assumptions for the radiative efficiency factor between radio and high-energy emission, this energy limit is consistent with the energies of the most powerful magnetar giant flares.
        Furthermore, the occurrence of most FRB sources inside star-forming galaxies supports an origin in magnetars formed via core-collapse supernovae. However, I will present the first ever localization of a repeating FRB far outside a quiescent galaxy, which challenges this theory. We propose that this source resides in a globular cluster, where the magnetar progenitor scenario is only viable if the magnetar formed via exotic formation channels such as compact-object mergers.

        Speaker: Ms Vishwangi Shah
      • 13:45
        An Aspherical Circumstellar Medium Surrounding Double-peaked Ic-BL SN2022xxf 10m

        Stripped-envelope core-collapse supernovae are the violent explosions that mark the death of a massive star that had some or all of its outer H and He layers stripped off. One class of stripped-envelope supernovae is the rare Type Ic-BL; these are the only events associated with the detection of a long-duration gamma-ray bursts, but it is still unclear why only some Ic-BLs accompany a gamma-ray burst detection. Radio observations probe the gas in the vicinity of a supernova, which contextualizes the lives of highly stripped stars and can tell us about which stars may produce a gamma-ray burst. In this talk, I will present radio observations of SN2022xxf, the nearest Ic-BL to date and discuss how its double-peaked light curve reveals the complex stripping mechanisms that shape these rare events.

        Speaker: Sam Lakerdas-Gayle (Cornell Center for Astrophysics and Planetary Science)
      • 13:55
        Mapping Magnetic Field Structure in Galactic Supernova Remnants with ASKAP 10m

        Polarization observations provide a unique opportunity to probe the geometry and structure of astrophysical magnetic fields. In the Milky Way, Supernova remnants (SNRs) are a key environment for connecting polarized emission to the physical processes tied to shaping the magnetic field: shocks, turbulence, and instabilities. By studying the organization of the on-sky polarization angle (PA) in SNRs, we are able to directly investigate the structure of the local magnetic field. Past radio observations of Galactic SNRs have been limited by sky coverage or resolution. However, with new observations from the Australian Square Kilometre Array Pathfinder (ASKAP) telescope, we are able to study the polarization properties of Galactic SNRs in unprecedented detail across the entire southern sky. Here, we present an in-depth study of the on-sky magnetic field structure for seven Galactic SNRs. We use radio polarization and continuum data from the Polarization Sky Survey of the Universe’s Magnetism (POSSUM) and the Evolutionary Map of the Universe (EMU) surveys. We derive on-sky magnetic field maps for the seven SNRs from the recovered intrinsic polarization angles. We also quantify the uncertainties in the intrinsic polarization angle measurements due to the differential rotation induced by the Faraday effect. Our on-sky magnetic field maps serve as an important foundation for future work mapping the three-dimensional magnetic field structure of the Galaxy.

        Speaker: Gabrielle Graham (University of Alberta)
      • 14:05
        Investigating Relativistic Jets in X-ray Binaries through Multi-Wavelength Timing Studies 10m

        Relativistic jets launched from accreting compact objects are thought to play an important role in the Universe, influencing large-scale processes such as galaxy evolution and star formation. However, the connection between their properties and those of the accretion flow remains poorly understood. Multi-wavelength time-domain observations of black hole X-ray binaries provide a new avenue to study this connection in detail. By probing different components of the system at different wavelengths, these observations allow us to trace the evolution of gas from inflow to outflow. Recently, we launched a first-of-its-kind observational program designed to obtain multi-wavelength time-domain observations spanning an entire X-ray binary outburst. In this talk, I will present the first results from this program, including recent ALMA and VLT observations of BW Cir (GS 1354-64).

        Speaker: Ms Élodie Lescure (University of Lethbridge)
    • 14:15 → 14:30
      Black holes & Instrumentation
      • 14:15
        Closing the AGN Feedback Loop Through Sub-kiloparsec Scale Gas Kinematics With JWST 1m

        Understanding how supermassive black holes influence the galaxies they inhabit remains a central challenge in astrophysics. The most massive galaxies in the Universe—Brightest Cluster Galaxies at the centers of galaxy clusters—offer an exceptional laboratory to study this connection. Immersed in vast reservoirs of hot gas, their central black holes both accrete surrounding material and release enormous amounts of energy, profoundly shaping the galaxy and its environment. The nearby Centaurus cluster, whose central galaxy is NGC 4696, provides a unique opportunity to observe this interplay in action thanks to its proximity and its spectacular network of cold gas filaments.

        In this talk, I will present new JWST/NIRSpec IFU observations that, for the first time, allow us to follow the entire feedback cycle linking black holes and galaxies—from gas cooling and condensation to accretion onto the black hole—across scales ranging from kpc down to pc. These observations reveal a rotating circumnuclear disk in NGC 4696 that is directly connected to the surrounding cold filament network. This structure provides the long-sought missing link that channels gas from kpc scales down to ~100 pc and ultimately into the central black hole, effectively closing the feedback loop. Comparisons with stellar kinematics further show that gas and stars respond very differently to the central gravitational potential and to feedback processes.

        These results provide new insight into how supermassive black holes shape their host galaxies and illustrate the transformative power of JWST for resolving the physical processes driving galaxy evolution.

        Speaker: Mathieu Marquis (Université de Montréal)
      • 14:16
        The Final Mass and Early Growth of the Intermediate-Mass Black Hole in Omega Centauri 1m

        Intermediate-mass black holes (IMBHs), with masses between $10^2$ and $10^5$$M_\odot$, may represent a missing link between stellar and supermassive black holes, yet few compelling candidates are known. In the Milky Way globular cluster Omega Centauri ($\omega$ Cen), Häberle et al. (2024) recently identified several stars near the cluster centre with projected velocities exceeding the escape velocity, implying the presence of a central compact object with a mass $M_\bullet$ ≳ $8\times$ $10^3 M_\odot$ and making it a strong IMBH candidate. We follow up on previous work in which we jointly modelled the orbits of the five most reliably measured fast-moving stars. Simultaneously fitting Keplerian orbits to their sky positions, proper motions, and line-of-sight velocities yielded an IMBH mass of $M_\bullet = (6.4^{+0.8}_{-0.7}) \times 10^4$ $M_\odot$. We predict that sky-plane accelerations for the three innermost stars will become detectable ($>3\sigma$) by 2030, which can confirm an IMBH and constrain its properties with greater precision. Our inferred mass agrees with Monte Carlo $N$-body simulations of $\omega$ Cen (González Prieto et al. 2025), which grow IMBHs to around ~ $50{,}000$$M_\odot$ over 12 Gyr from initial black hole seeds of $500$ - $5000$$M_\odot$. However, the formation mechanisms for such massive seeds early in the cluster's evolution are an open question. Using rapid cluster-evolution models motivated by the initial conditions of $\omega$ Cen, we identify viable seed-formation pathways through runaway stellar collisions and hierarchical black hole mergers.

        Speaker: Mackenzie Hayduk (Saint Mary's University)
      • 14:17
        Catching Emission "Life-Lines" in Black Hole X-ray Binaries to Understand Relativistic Jets 1m

        Stars are rarely born alone, often existing in pairs. When one of these stars reaches the end of its life, it can collapse into a black hole, creating a black hole X-ray binary where it feeds off the matter of its companion star. This material spins rapidly, creating a hot accretion disk (emitting X-rays) while also launching powerful, outflowing jets (emitting radio waves). To understand how these jets form, this project uses data from the Atacama Large Millimetre Array (ALMA) to identify spectral emission lines, which trace where the jets slam into the interstellar medium. It was necessary to automate high-volume retrieval, processing, and production of calibrated datasets through a custom pipeline to identify spectral emission line signatures utilizing Common Astronomy Software Application (CASA) packages. These lines are then mapped with radio astronomy imaging techniques to deconstruct jet formation and energy.

        Speaker: Aadi Patel (University of Lethbridge)
      • 14:18
        Dynamical Simulations of Self-Consistent Mass Accretion onto Black Holes in Ultralight Dark Matter 1m

        Dark matter may be made of ultra-light bosonic particles, so light that it behaves like a large-scale quantum wave rather than a swarm of individual particles ("ultralight" or "fuzzy" dark matter). This wave nature changes how massive objects like black holes move through it: the drag that normally causes objects to sink toward a galaxy's center can behave very differently.

        Prior work on a black hole moving through this kind of dark matter found strikingly different outcomes depending on the environment. Embedded in the dense, wave-supported core at a galaxy's center, the black hole doesn't simply sink; its orbit oscillates in a "stone-skipping" pattern as it repeatedly disturbs and rebounds off the vibrating core (Zhang, Wang, Zagorac & Easther 2026). In a smoother, more uniform environment, our own preliminary work instead finds enhanced dynamical friction due to the formation of a dense gravitational wake.

        Such prior work was based on dynamical simulations where we held the black hole's mass fixed, which while arguably a small effect, still isn’t complete given the vast timescales of a cosmological simulation. We add the missing piece: a black hole should also grow by swallowing the surrounding dark matter as it moves. We implement a physically calibrated accretion prescription, matched to the classical accretion rate used throughout astrophysics for objects moving through gas. The new tool also gives the black hole a physical momentum kick from the infalling matter, not just added mass. We present early results on how this self-consistent growth changes the dynamics in both environments considered before.

        Speaker: Yourong Frank Wang (University of Göttingen)
      • 14:19
        Neural Network Classification of BL Lacs and FSRQs among X-ray/Gamma-ray Blazars discovered in the Fermi 4FGL-DR4 Unassociated Catalog 1m

        Of the 2423 unassociated sources in the fourth data release of the fourth Fermi Large Area Telescope catalog (4FGL-DR4), 748 had also been observed by the Neil Gehrels Swift Observatory's X-ray telescope for $>4$~ks. Neumann et al. (2026) recently used a neural network classifier to identify new local pulsars and high-energy blazars from these unassociated sources, and they classified 173 likely blazars from $\gamma$-ray sources with singular X-ray counterparts. We adopt these new likely blazar singlets, along with the 4FGL-DR4 blazar candidates of uncertain types, to search for further classifications of 281 total sources into BL Lac (BLL) and flat spectrum radio quasar (FSRQ) categories. From those 281 sources, 218 of them had not been previously analyzed by an earlier attempt to classify blazars into these dominant sub-classifications (Kaur et al. 2023). Using infrared to $\gamma$-ray parameters, we identify 136 likely BL Lac objects (Probability of BLL, $P_{\text{bll}}>0.99$) and 29 likely FSRQs (with $P_{\text{bll}}<0.01$) using a multilayer perceptron neural network classifier, while the remaining 116 sources remain ambiguous. A majority of these new sources are observationally much fainter than existing sources, by one or two magnitudes, enabling a direct probe into the lower-flux region of the existing blazar population. We propose further investigation into the optical spectra of these new, faint FSRQs to obtain spectroscopic confirmation and redshift estimates. Confirming these new sources will test how far into the observationally faint-source region the FSRQ population extends, and when coupled with redshifts, have the potential to extend the low-luminosity end of the blazar sequence.

        Speaker: Sierra Deppe (McGill University, Penn State University)
      • 14:20
        Making Reconnection Cooler: Modelling bright emission around black holes 1m

        Accretion disks around black holes, such as those in active galactic nuclei and X-ray binaries, are home to extreme plasma processes that produce bright emission across the electromagnetic spectrum. One such process powering this emission is thought to be magnetic reconnection, the violent restructuring of the magnetic field topology in which magnetic field lines pinch apart and reconnect, converting stored magnetic energy into kinetic energy of the encompassing plasma. In particular, magnetic reconnection may be responsible for high-energy X-ray emission from a hot “corona” near the central black hole. In this talk, I will demonstrate how this emission is modelled computationally in relativistic magnetohydrodynamic simulations, as a step towards unlocking the theory behind these fascinating astrophysical environments.

        Speaker: Alicia Savelli (University of Toronto)
      • 14:21
        Modelling Variable Broad Absorption Line Quasar Outflows Using SimBAL 1m

        Active galactic nuclei (AGN) are supermassive black holes in the centers of massive galaxies with large inflows of gas and dust collisionally heating up and radiating away energy. Quasars are a type of AGN that outshine their host galaxies by several magnitudes, capable of releasing high velocity outflows (or winds) of material due to the intense radiation being emitted. When these outflows are directed along the observer's line of sight, their ultraviolet spectra will present with broad absorption lines (BALs). These types of objects are categorized as BAL quasars, and these BALs in their spectra have been observed to vary over time for select quasars. The origin of this variability is not yet fully understood, though spectral fitting algorithms such as SimBAL (Leighly et al., 2018) have proven successful in modelling the physical properties of quasar winds using a forward-modelling and Markov Chain Monte Carlo approach. This software package fits synthetic spectra to observed spectra for a given quasar, producing detailed physical and kinematical descriptions of these outflows. The fits of these spectra constrain the values of parameters including the density integrated along the line of sight (column density), the ionization of the outflows (ionization parameter), and the obscuration of the quasar's radiation from intervening clouds (covering fraction). My quasar of choice for modelling using SimBAL has three epochs of available data from the Sloan Digital Sky Survey, each separated by six years. The earliest epoch has the widest and deepest absorption lines for Carbon IV, Silicon IV, and Lyman Alpha, however for each later epoch the lines are becoming weaker and narrower. As of now, the leading candidates for the source of the BAL variability appear to be the column density and the ionization parameter. The relative impacts of each parameter on the differing absorption structure are yet to be determined, and that will be the next focus of my master's work.

        Speaker: Nicolas Frisella (Western University)
    • 14:15 → 14:30
      Exoplanets & Stars: Flash talks
      • 14:15
        Forecasting The Weather On Ultra-Hot Worlds: A High-Resolution Study of WASP-189b 1m

        Exceeding temperatures of up to 3,300K, WASP—189b's dayside hemisphere is a unique laboratory in which we can probe the extreme atmospheric conditions experienced by the population of ultra-hot Jupiter (UHJ) exoplanets. Using high-resolution observations from GHOST on Gemini South, we detect various metals within WASP—189b's atmosphere, alongside a first tentative detection of neutral potassium using the Doppler cross-correlation method. Our work details the exploration of using such detections to study atmospheric patterns on this planet, providing a first step toward forecasting global weather conditions.

        Speaker: Mr Jason Gabriel (University of Waterloo)
      • 14:17
        Rapid Rotation of a Cold Extremely Metal-poor Brown Dwarf 1m

        We report the first detection of brightness variability in an extremely metal-poor brown dwarf. These objects are ancient, very low-mass members of the Milky Way that formed when the Galaxy contained far fewer heavy elements than it does today. Using the 10.4-m Gran Telescopio Canarias, we found that the nearest known extreme T subdwarf, WISEA,J181006.1$-$101000.5, changes its $J$-band brightness by $1.14\pm0.26%$ every $73.7\pm1.5$ minutes. We interpret this periodic signal as the rotation of an uneven atmosphere into and out of view. The object completes a rotation about 8 times faster than Jupiter, similar to watching changing cloud patterns on a rapidly rotating Jupiter. An independent measurement of its projected rotational velocity, $v\sin i = 125^{+25}_{-23}\ {\rm km,s^{-1}}$, confirms that the object is an extremely fast rotator. Such rapid rotation may be a natural consequence of its old age and compact size: unlike stars, these ultracool objects have no efficient mechanism to slow their rotation over billions of years. This first detection opens a new window into the atmospheres and rotation of the oldest ultracool objects in the Galaxy.

        Speaker: Jerry J.-Y. Zhang (Western University)
      • 14:19
        Searching for Precursor Outbursts in 2024jlf 1m

        Type IIn supernovae (SNe) are a subclass of Type II SNe characterized by narrow hydrogen emission lines produced by interactions between SN ejecta and surrounding circumstellar material (CSM). Some Type IIn SNe show these features only briefly, indicating less extended CSM and motivating their classification as Type IIn-like SNe. The origin of this CSM remains a major outstanding question.

        Precursor outbursts are episodes of enhanced mass loss from a progenitor prior to explosion theorized to contribute to CSM formation. They have been observed in approximately 25–50% of Type IIn SNe, but only one Type IIn-like progenitor has been linked to precursor activity. We therefore investigate possible pre-SN variability in the progenitor of the Type IIn-like SN 2024jlf.

        Using data from the ATLAS Forced Photometry Service, we applied the ATClean pre-SN variability analysis pipeline. ATClean cleans progenitor and control light curves, searches for sustained signals across Gaussian-kernel timescales, and estimates detection efficiency by injecting simulated precursor outbursts into controls.

        ATClean detected sustained pre-SN signals across all tested timescales. Binning the cleaned progenitor light curve revealed >5σ detections in the same time range. However, difference images revealed variability in a nearby image artefact during the epoch of detections, and ATClean’s binning procedure is susceptible to outliers.

        Future work such as investigating the above artefacts and refining the ATClean binning procedure is needed to determine the exact source of our detections, thereby constraining pre-SN mass loss in IIn-like systems.

        Speaker: Ms Ai Hua Li (Dunlap Institue for Astronomy & Astrophysics)
      • 14:20
        First Mid-Infrared Characterization of the Galactic Center WR Star Population 1m

        This research presents the first mid-infrared characterization of the Galactic Center (GC) Wolf-Rayet (WR) and Ofpe/WN9 star population using integral-field spectroscopy from the JWST Mid-Infrared Instrument MRS. Data consist of calibrated, three-dimensional FITS spectral cubes spanning λ∈[4.9, 27.9] μm at resolving power R∈[1330, 3750]. As an initial application, the spectrum of the Ofpe/WN9 star IRS 16NW is analyzed in Channel 1, being corrected for extinction, foreground H₂O rovibrational absorption, defects, and back/foreground emission. Spectral features are identified and deblended with multi-component Gaussian or quartic fits, then assessed for association with IRS 16NW using measurements of its line-of-sight velocity and expected line width.

        WR and Ofpe/WN9 stars undergo radiatively driven mass loss through stellar winds. Expelled material from approximately 30 WR or Ofpe/WN9 stars is consistent with supplying all material available for accretion onto Sgr A; wind metallicity can therefore have implications for the accretion rate: higher metal abundances enhance radiative cooling, allowing shocked winds to lose thermal pressure support and reach smaller radii. By identifying the intrinsic mid-IR spectral contributions of these stars and separating them from surrounding GC structures, the analysis further constrains the composition/metallicity of the accretion environment of Sgr A. Metal-line ratios are derived either directly from detected stellar emission or, for non-detections, constrained using Monte Carlo injection-recovery tests.

        Speaker: Zachary Ireland (University of Toronto)
      • 14:21
        Tracing Star Formation Histories in the Local Neighborhood using Young Stellar Associations 1m

        Young stellar associations provide an opportunity to investigate the recent star formation history of the Solar Neighborhood by identifying groups of stars that share similar ages and kinematic properties. In this work, I investigate two nearby young stellar associations, SCYA 75 (Ophiuchus Southeast) and SCYA 103 (Scorpius-Centaurus), to explore whether their stellar populations show evidence of differences in their formation histories. I used a local k-neighborhood search to identify nearby stellar members and characterize the local stellar populations associated with each region. I then compared the age distributions and statistical properties of the identified populations to investigate similarities and differences between the two associations. By examining the ages of stars in these neighboring regions, this study aims to provide insight into the timing and structure of recent star formation in the local solar environment. This approach demonstrates how spatially localized stellar population searches can be used to connect individual young associations to the broader star formation history of the Solar Neighborhood.

        Speaker: Ms Sargun Jassal (University of Toronto)
      • 14:22
        Reshaping the Search for Substructures in Young Protostellar Disks 1m

        To date, ALMA has conducted thousands of protostellar disk observations, and studying this archive has revealed much about the nature of these dusty disks around infant stars. Including that many of even the youngest disks contain an indicator of planet formation: axisymmetric substructures. However, the high computational/observational requirements of current methods mean only a small portion of disks have been examined for substructures. My work aims to investigate the prevalence of substructure in young disks by developing a neural network that uses Simulation-Based Inference (SBI) to quickly identify features such as gaps and rings directly from ALMA’s raw uv visibilities.

        Thus, I have built a data pipeline that creates a training dataset of visibilities by combining real observations of disks with known substructures alongside synthetic observations of real and simulated disks. The thousands of simulated disks are generated with a range of substructures, from simple smooth disks to ones with multiple gaps and rings, and each one is synthetically observed with a range of positional and observational parameter values. This variety ensures that the dataset mimics the breadth of qualities found across real observations.

        Once this SBI model is complete, it will be able to identify a disk’s most likely substructure(s) in seconds, instead of the hours required by conventional techniques. By creating this model and running it over every viable young disk in ALMA’s archive, I aim to shift the current paradigm from analysing individual disks to analysing the presence, form, and statistics of substructure among large disk populations.

        Speaker: Ms Sullivan Callista (Queen's University)
      • 14:23
        Finding Young Stars in the Noise: A Multi-Wavelength Detection and Classification Algorithm for Young Stellar Objects 1m

        Young Stellar Objects (YSOs) range from the beginning of star formation (protostars) up until the beginning of the main sequence (T Tauri stars). By looking at the inception of the formation process, we can gain insight into stellar evolution, star-forming regions and their structures, and the motion of stars and surrounding matter. Using the Orion star-forming complex as a primary testing ground, we build an algorithm designed to detect YSOs and their evolutionary subclasses in arbitrary regions of the sky. The algorithm combines near-infrared photometry from 2MASS, soft X-ray detections from eROSITA DR1, astrometric measurements from Gaia DR3, MIST isochrones, and mid-infrared photometry from AllWISE and, where available, Spitzer SEIP. Mid-infrared YSO selection follows the Koenig & Leisawitz (2014) and Gutermuth et al. (2009) schemes, with Spitzer taking priority over WISE when classifiable data are available. Candidate populations from infrared, X-ray, and Gaia branches are merged and assessed using complementary youth indicators. Across six independent star-forming clouds, the final mid-infrared classifier recovered approximately 82% of YSOs with sufficient photometry for classification. For Class 0/I protostars, conditional recovery reached 69.8%, while classification agreement among recovered protostars and Class II sources was approximately 95%. Most missed protostars were limited by catalogue availability or unclassifiable photometry rather than colour-selection failure. These results demonstrate both the effectiveness of literature-based infrared classification when suitable data are available and the importance of combining complementary youth diagnostics to construct a portable, all-sky YSO-selection algorithm.

        Speaker: Mr Luke Sacco (University of Toronto/University of Hertfordshire)
    • 14:15 → 14:30
      Galaxies, Gas/dust, Solar system & Stars: Flash talks
      • 14:15
        Fifteen Years of Archival ALMA Data as a Survey: A Search for Accretion Streamers in Serpens Main 1m

        Protostellar accretion streamers are coherent filamentary structures that channel material from envelope scales and beyond into protostellar cores. Largely found serendipitously, streamers have emerged as a potentially important yet poorly characterized mode of mass assembly in early star formation, with occurrence rates, class dependence, and environmental dependence still unconstrained. ALMA-SAILS (ALMA Search for Asymmetry and Infall at Large Scales) addresses this by treating nearly 15 years of the ALMA Science Archive as a survey. Data taken for other science goals are uniformly reprocessed on CANFAR into a single, self-consistent dataset at no additional observing cost. Our pilot study targets Serpens Main, combining 96 datasets from 43 ALMA projects (Bands 3–8, Cycles 2–11). Uniform self-calibration and imaging yields ~200 continuum images across 59 targets. Emission is detected toward 43 of them. About 20 (47%) show extended or asymmetric structure rather than a compact core, and ~10 exhibit extended features ≥2000 au, which suggests infall from beyond the dense core. Cross-matching with protostellar catalogs lets us compare candidate fractions across evolutionary stages. Since continuum morphology cannot confirm infall, we also run automated line identification across 881 line-bearing spectral windows. We confirm 112 detections of dense-gas and infall tracers toward 24 sources. We present our first kinematic results toward the strongest candidates, using SCOUSE and ACORNS to isolate coherent velocity structures, while noting a key limit of archival data: over a third of spectral windows are too coarse (>5 km/s) to resolve streamer velocity gradients.

        Speaker: Mr Samuel Fielder (University of Victoria)
      • 14:16
        From Starless Cores to Embedded Disks: Chemistry and Fragmentation in Early Star Formation 1m

        The physical and chemical conditions present during planet formation are established during the earliest embedded Class 0/I phases of star formation. At this stage, protostellar systems are still being shaped by infall, outflows, irradiation, and chemical processing. Understanding how these processes set the initial conditions for star and planet formation requires observations that can resolve the small-scale structures within embedded systems. We present the first systematic high-angular resolution (0.1”, ~15 au) study of disk-scale chemistry in 19 nearby embedded protostars as part of the ALMA Large Program eDisk. Using multiple molecular tracers, we identify the distinct morphologies within these young systems. $^{12}$CO and SiO trace outflows and jets, while $^{13}$CO and C$^{18}$O trace rotating inner envelope and disk regions. The compact hot core regions are traced by DCN and CH$_{3}$OH, and are particularly prominent towards the youngest Class 0 sources. Hydrocarbons are associated with UV-irradiated outflow cavity walls, while SO and H$_{2}$CO show complex morphology, tracing various structures that include non-axisymmetric infall through streamers. Recently, we are using archival ALMA observations to investigate fragmentation in dense starless cores. This complementary study probes the structures that precede protostellar formation and will help connect the initial fragmentation of dense cores with the physical and chemical complexity observed in young embedded systems. Together, these efforts will provide a more complete view of the initial conditions of star and planet formation.

        Speaker: Rajeeb Sharma (Herzberg Astronomy and Astrophysics)
      • 14:17
        Quantifying the Effect of a Bottom-Light IMF on Globular Cluster Evolution Using the Cluster Monte Carlo Code 1m

        The distribution of stellar masses within a globular cluster (GC) at the time of formation, referred to as the Initial Mass Function (IMF), is directly linked to the evolution of the cluster, including the rate of binary black hole (BH) mergers that produce gravitational waves. Recent studies suggest that GCs may have formed with a bottom-light IMF, meaning fewer low mass stars and more BH progenitors per unit cluster mass compared to the standard Kroupa (2001) IMF. In this study, we evolve a small set of simulated GCs with a bottom-light IMF using the Cluster Monte Carlo code, which models the dynamical interactions between stars, the formation and retention of compact objects and the large-scale evolution of the cluster mass and radius. We then compare the evolutionary data to an identical set of clusters formed with the standard Kroupa IMF to quantify the effect of the varying mass distribution. By analysing properties including black hole populations, cluster mass and radius over time, we investigate whether a bottom-light IMF produces properties of evolved GCs that differ significantly from those produced by a Kroupa IMF. The results of these simulations can be compared to current photometric observations to inform future work surrounding the IMF and help revise predictions for the rates of binary BH mergers originating in GCs.

        Speaker: Kristen Cowan (Saint Mary's University)
      • 14:18
        Extragalactic Probes for a Galactic Model: Validating the NE2025 Galactic Electron Density Model using CHIME Fast Radio Bursts Scattering Measurements 1m

        Models of the Galactic electron density are widely used to predict distances and scattering of compact radio sources, and to account for interstellar medium foregrounds in extragalactic studies. The recently updated NE2025 model (Ocker & Cordes 2026) offers improvements over its predecessor, the commonly referenced NE2001. However, its scattering predictions have yet to be tested by extra-galactic sources. In this talk, I will present a direct test using fast radio bursts (FRBs) detected by CHIME/FRB. Since FRB signals propagate through the full Galactic interstellar medium, their observed scattering must equal or exceed the Milky Way contribution, making them natural constraints on Galactic scattering models. Using CHIME/FRB baseband data, we measure scattering timescales at microsecond-to-millisecond precision and compare them to the NE2025 prediction along each line of sight. I will show that while most FRBs are scattered well beyond the Galactic prediction, a subset of minimally scattered FRBs place hard upper limits on the true Galactic scattering, clustering in a region of overestimation by NE2025 . I will discuss what these sightlines can reveal regarding specific model parameters, and the outlook for using FRBs to calibrate future models.

        Speaker: Daniel Amouyal (McGill University)
      • 14:19
        The Impact of Inspiral Timing and Model Assumptions on Convective Common Envelopes 1m

        Common envelope (CE) evolution occurs when one, often more massive, star in a binary system completely engulfs a nearby companion. The companion continues its inspiral inside the shared envelope, leading to one of two outcomes: the companion merges with the primary star, or its liberated orbital energy unbinds and ejects the envelope. In the latter case, the ejection of the envelope leaves behind a tight binary; this process is thought to be the primary formation mechanism for both thermonuclear supernova and gravitational wave progenitor systems. However, population synthesis codes often fail at reproducing the observed population of these systems, highlighting gaps in our physical understanding of the CE phase. In this work, we study the physics of CE evolution by using a convective CE model, which accounts for the redistribution of energy by convection within the primary, where inspiral energy liberated in a convection-dominated zone is lost via convection and radiation. We extend previous research by investigating how the specific convection models assumptions adopted in the stellar evolution code MESA impact the predictions for the outcome of CE evolution along the asymptotic giant branch (AGB). We find that differences in stellar structure caused by variations in the adopted convective parameters can lead to drastic differences in the predicted CE efficiency (and therefore final binary separation), particularly for binaries with large initial separations which enter the CE towards the end of the primary’s AGB phase.

        Speaker: Ms Chaudhuri Aishani (University of Toronto)
      • 14:20
        Unveiling the Origins of a Historic Supernova 1m

        The nature of historical supernovae is often unknown, but supernova remnants and their environments can serve as powerful tools for probing the progenitor system. RCW 86 is a peculiar supernova remnant, thought to be associated with the historical supernova SN 185. A prevailing theory is that it was a cavity explosion, leading to questions about the nature of the progenitor system. To better characterize this supernova remnant, long-slit spectroscopic data of RCW 86’s expanding shock front were gathered in 2025 using the 8.1-meter Gemini South telescope. The data were reduced via the Gemini DRAGONS pipeline, with the goal of measuring the ionized hydrogen and helium fluxes and converting them into surface brightnesses. CLOUDY (1D photoionization simulation software) models were run for two different models: a blackbody model and a stripped-envelope model. The blackbody model represents thermonuclear runaway supernovae, as a white dwarf accretes matter from a companion star, whereas the stripped-envelope star model represents core-collapse supernovae. The surface brightnesses of these models were compared with the observed surface brightnesses, and the models were constrained accordingly. The temperature and luminosity of the blackbody sources were constrained to models with high temperatures and low luminosities. The mass and luminosity of the stripped-envelope star model was constrained to ~4 M$\odot$ and ~2.5 L$\odot$, respectively. With this work we have placed novel constraints on the progenitor of RCW 86.

        Speaker: Ms Amilia Petryk (University of Manitoba)
      • 14:21
        From Starlight to Synapses: How Cosmological Bayesian Inference Reveals the Brain's Molecular Structure 1m

        Super-resolution microscopy is a rapidly evolving field, and analytical tools are struggling to keep up with novel imaging techniques. 'MINFLUX' (minimal fluorescence photon fluxes) is one such technique; it uses targeted emission to track molecules down to the nanometer scale. However, 'MINFLUX' outputs localizations of these molecules rather than viewing the protein superstructure directly, leaving a gap for a tool that can make that leap. 'AstroPhot' is a Bayesian framework traditionally used to analyze and deblend crowded/transient cosmological data by separating objects and fitting parameters individually. With some unifying adjustments, 'AstroPhot' can be calibrated to ingest MINFLUX data and fit shared parameters across objects to fit greater protein superstructure based on molecular localizations. This approach is tested against 'MINFLUX' data from neural inhibitory synapses, where the hexagonal lattice structure of the gephyrin protein is analyzed. Gephyrin is crucial in the regular function of the brain; mutations and abnormalities in gephyrin are linked to epilepsy, Alzheimer's, and schizophrenia. The natural superstructure formed by gephyrin in the brain is debated throughout the literature. Thus, understanding gephyrin structure and applying the approach used to other proteins is key to tackling some of the longstanding neurological disorders plaguing humanity.

        Speaker: Manveer Sidhu (Ontario Tech University, Dunlap Institute for Astronomy and Astrophysics)
    • 14:15 → 14:30
      Galaxies: Flash talks
      • 14:15
        Constraining the Effects of Feedback on Diffuse Gas with Hydrodynamic Simulations 1m

        Feedback from stars and Active Galactic Nuclei (AGN) plays an important role in galaxy formation, impacting star formation and gas conditions across a range of physical and temporal scales. Hydrodynamic cosmological simulations rely on feedback to match observations of global properties of galaxies, but they vary dramatically in their treatment of the underlying physical mechanisms. One promising means of better constraining AGN feedback models is through the circumgalactic medium (CGM). In this talk, I will begin by exploring how the AGN feedback prescriptions in a range of cosmological simulations shape the CGM. I will assess the observability of these differences by generating mock thermal Sunyaev-Zel’dovich and X-ray observations and comparing them against stacked CGM observations. In the second half of this talk, I will share my work using high resolution X-ray spectroscopy from the XRISM telescope to test AGN feedback models at larger mass scales, exploring the dynamics of the intracluster medium. I will also talk about how XRISM has impacted our understanding of stellar feedback processes, using observations of the starburst galaxy M82 to test longstanding models of supernovae-driven winds.

        Speaker: Skylar Grayson
      • 14:18
        Probing the Physical State of Warm Gas in NGC 4696: Infrared Diagnostics for the JWST Era 1m

        How do supermassive black holes (SMBHs) regulate the growth of the most massive galaxies? The cycle of gas cooling and AGN feedback is central to this question, yet the physical state of the "warm" multiphase gas often remains elusive. In this talk, I present JWST/NIRSpec IFU observations of the inner 640 pc of NGC 4696, the prototypical BCG of the Centaurus cluster. These data reveal dozens of atomic and molecular emission lines, including a rich set of H₂ rovibrational transitions that trace spatial variations in excitation mechanisms at unprecedented resolution. Using Cloudy simulations, I develop new infrared diagnostics, analogous to optical BPT diagrams, optimized for JWST observations.
        These results provide new insights into the physical state and excitation of warm gas in massive galaxies and demonstrate the broader potential of JWST spectroscopy for probing feedback, cooling, and star–black hole coupling across different environments. This work highlights Canada’s significant role in JWST science and its contribution to advancing infrared galaxy evolution research, fostering pride in our scientific community.

        Speaker: Ms Olivia Pereira (Université de Montréal)
      • 14:19
        SMA observations of the archetypal CSS radio source 3C 303.1 1m

        AGN (active galactic nuclei) feedback plays a crucial role in shaping galaxy evolution. Numerical simulations show that the kinetic energy transfer efficiency from radio jets to interstellar medium (ISM) is relatively high, suggesting a significant role of radio jets in the feedback. We investigate AGN feedback on cold gas in the compact steep-spectrum (CSS) radio source 3C 303.1. CSS sources are largely young radio galaxies evolving through dense environments of their host galaxies. This early evolutionary phase likely represents a critical stage in which the radio source has maximum impact on host galaxy evolution. 3C 303.1 is the only CSS source so far showing alignment in optical, X-ray and UV with the radio structure, making it an interesting source to investigate jet-feedback. We present continuum and spectral line observations of the J=3-2 transition of carbon monoxide ($^{12}$CO) of 3C 303.1, obtained with the Submillimeter Array. We detect continuum emission at 221.1 and 271.2~GHz. We do not detect the $^{12}$CO(J=3-2) line and derive an upper limit on the molecular gas mass of $\sim 2.3 \times 10^{9}\ \mathrm{M_\odot}$. The gas-to-dust mass (G/D) ratio is found to be at the lower end of typical Galactic values, and the star-formation rate (SFR) derived is moderate but declining likely due to a recent quenching event. Therefore, $^{12}$CO(J=3-2) non-detection, relatively low G/D ratio, and the moderate but declining SFR point to the shock-heating and/or removal of CO gas by AGN, consistent with the AGN feedback signatures observed in 3C 303.1.

        Speaker: Mr Rushikesh Bhutkar (University of Manitoba)
      • 14:20
        Initial Investigations of the Outskirts of XLSSC 122 1m

        We investigate the redshift 1.98 galaxy cluster XLSSC 122 using the Hubble Space Telescope (HST) from the core of the cluster out to 3 Mpc, a scale equivalent to 10 times the R500 = 295 kpc radius. We present an expanded photometric and spectroscopic catalogue of the cluster, bringing the total number of spectroscopically classified member galaxies to 74, with 35 new member galaxies added in the outer regions of the cluster. We compute the radial galaxy number density profile in the cluster, and observe no clear evidence of infalling groups or cosmic filaments. We observe a clear bimodal colour relation in member galaxies, with red fraction increasing towards the cluster centre. This rapid increase of red fraction upon infall is indicative of a fast quenching mechanism, such as ram pressure stripping, as galaxies enter the cluster centre. We fit a luminosity function to the cluster members, finding a similar low mass slope but fainter scale magnitude than z = 1 clusters of similar temperature, implying a similar galaxy evolution rate to clusters at lower redshift. These findings indicate that XLSSC 122 is experiencing an evolutionary process not typically observed in high redshift clusters, and is more similar to z = 0 clusters.

        Speaker: Eleanore Todd (University of Victoria)
      • 14:21
        Bulge-driven quenching in KILOGAS: separating classical bulges, pseudobulges and disks with SPADE 1m

        Bulges are implicated in quenching, but which bulges, and how they quench galaxies (gas-driven or efficiency-driven), remain open questions. We present SPADE (Spectro-Photometric Analytic Decomposition Engine), a new method that fits imaging, integral-field stellar kinematics and stellar-population spectra of a galaxy simultaneously under one likelihood to separate a bulge from a disk, and uses the joint evidence to distinguish classical bulges from pseudobulges. We apply SPADE to 450 galaxies from KILOGAS, an ALMA CO(2-1) survey at kiloparsec resolution of MaNGA and SAMI galaxies, assigning every star-forming, green-valley and quiescent galaxy a bulge type and every spaxel a bulge or disk membership. Combining this with the resolved star-forming main sequence, molecular gas main sequence and Kennicutt-Schmidt relation, we measure how far classical bulge, pseudobulge and disk regions deviate from these resolved scaling relations as a function of radius. We then decompose the specific star-formation-rate deficit into a gas-fraction term and a star-formation-efficiency term. Classical bulges in green-valley galaxies fall well below their own disks in star formation, and most of that deficit is a loss of efficiency rather than of gas, driven by a growing fraction of regions that have stopped forming stars. Pseudobulges show no such suppression, and the gas deficit that does exist is concentrated in regions where CO is undetected. These results favour quenching that begins inside classical bulges as a failure to convert gas into stars, with gas loss following rather than leading.

        Speaker: Angelo George (ASIAA)
      • 14:22
        Bayesian and Brisk: Scalable AGN Lightcurve Simulation and Fitting for Supernova Cosmology and Population Studies 1m

        Active Galactic Nuclei (AGNs) are dense, bright regions at the centre of galaxies thought to be caused by matter accreting into a supermassive black hole. Millions of AGNs have been observed, and population-level studies are needed to learn about AGN physics.

        On the other hand, AGNs can be contaminants in cosmology. Type 1a supernovae are frequently used as “standard candles” to infer cosmological parameters by estimating both their redshift and distance modulus to trace cosmic expansion. The Legacy Survey of Space and Time (LSST) will observe millions of supernovae photometrically. Since few Type 1as will be spectroscopically confirmed, other transients can be confused for Type 1as due to low cadence and different sources of uncertainty, such as instrument noise and model uncertainty. All sources of uncertainty, including the uncertainty in the label of the source, must be propagated throughout the model in a fully Bayesian manner to acquire credible intervals for the inferred cosmological parameters. This is what the package Cosmographi aims to do, while remaining scalable by using JAX.

        This work will present the forward model and fitting modules for AGNs within the Cosmographi framework. The user will be able to produce simulated lightcurves orders of magnitude faster compared to pre-existing methods. Moreover, it allows for fully Bayesian lightcurve fitting, and inference of cosmological parameters from a population with different types of transients.

        In conclusion, we present advances towards a fully Bayesian estimation of cosmological parameters from millions of supernovae, and population-level studies of AGNs.

        Speaker: Ms Zoe Augspach (University of Toronto)
      • 14:23
        Mapping the Faint Frontier: Improved Local Group Kinematics with JWST + Gaia + HST Astrometry 1m

        Stellar proper motions (PMs) are fundamental for reconstructing the Local Group dynamics, understanding the Milky Way accretion history, and constraining the nature of dark matter. While Gaia is powerful for measuring PMs, its performance is limited for faint sources (G > 20 mag). Previous studies on Gaia + Hubble Space Telescope (HST) astrometry have shown that combining telescopes achieved more precise PM measurements than Gaia alone.

        Motivated by GaiaHub, a previous Gaia + HST tool, we have developed GaiaWebb, which combines Gaia and James Webb Space Telescope (JWST) observations. GaiaWebb retrieves JWST images, extracts stellar positions and magnitudes, cross-matches JWST sources with Gaia stars, aligns JWST images to the Gaia reference frame, and then measures the improved PMs using large JWST-to-Gaia time baselines. We have also expanded another Gaia + HST tool, BP3M (Bayesian Positions, Parallaxes, and Proper Motions), to simultaneously combine JWST + Gaia + HST measurements. The enhanced BP3M differs from GaiaWebb in that it uses Gaia data as priors while jointly aligning images and making measurements. We tested our new tools on the Large Magellanic Cloud and Draco dwarf galaxy, and the resulting PMs are consistent with the literature measurements. GaiaWebb and BP3M improve PM precision by factors of 5-20 compared to Gaia DR3 alone, with faint stars (G > 19 mag) seeing the largest improvement.

        Our future work will include producing publicly available catalogues of improved PMs, calibrating those catalogues through comparisons with the literature, and measuring new bulk motions of Local Group structures.

        Speaker: Ms Liwen Chen (University of Toronto)
    • 14:15 → 14:30
      Transients & Cosmology: Flash talks
      • 14:15
        Modelling the Energy and Redshift distribution of FRBs using the Second CHIME/FRB catalog 1m

        Fast radio bursts (FRBs) are energetic millisecond-duration bursts with extragalactic origins. Roughly 4000 unique sources have been observed to date, about 3% of which have been seen to repeat, though it remains unclear whether all FRBs repeat.
        An FRB population study addresses several key questions: How often do FRBs occur in the universe? What energy and redshift distributions do they follow? Is their occurrence correlated with the cosmic star formation history (SFH)? Answering these questions helps contextualize the origins of FRBs with potential astrophysical sources such as magnetars and supernovae.
        Previous population studies, based on samples of a few hundred sources, have provided important constraints on FRB rates and energetics. However, these analyses were limited by smaller sample sizes, less well-characterized selection effects, and uncertain treatment of repeat bursts.
        The recently released Second CHIME/FRB Catalog contains more than 90% of all known FRB sources (≈3600) and provides well-calibrated selection effects. We leverage this sample to infer key FRB properties, including the volumetric rate, energy function, redshift distribution, and correlation with the cosmic SFH. We then compare the predicted energetics and abundances with proposed FRB models and contrast the inferred redshift distributions with those of FRBs with known host galaxies.

        Speaker: Naman Jain (McGill University)
      • 14:16
        Characterizing Fast Radio Burst morphologies in CHIME’s Baseband Catalog 2 1m

        Fast radio bursts (FRBs) are millisecond-duration radio transients originating at extra-galactic distances. Their morphologies, the signal’s evolution as a function of time and frequency, encode valuable information about their emission physics as well as intervening plasma and magnetic fields. For example, we aim to measure the temporal spacing between sub-bursts, their changes in bandwidth and their asymmetry. This constrains theoretical emission models and provides direct measurements of the column density and clumpiness of ionized matter along the line of sight. Two main streams of data are recorded by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope: intensity at 1ms cadence and raw voltage (baseband) at 2.56µs cadence. CHIME recently released its second Catalog of FRBs at intensity resolution, containing over 4500 events. The upcoming Baseband Catalog 2 of CHIME includes a sample of Catalog 2 FRBs, containing over 2000 events, allowing us to study a population of multi-component and complex events. In this talk, I will present our current morphology pipeline using fitburst, a least-squares fitter that uses both exponentially modified Gaussian sub-bursts and a running power law. I will present preliminary results obtained with this pipeline and show correlations between different morphological parameters.

        Speaker: Chloé Legué (McGill University, Trottier Space Institute)
      • 14:17
        Sub-band Extensions to Measure Scattering with the Arrival-Times Pipeline for Repeating Fast Radio Bursts 1m

        Fast radio bursts (FRBs) are millisecond-duration extragalactic radio transients, a subset of which repeat. Multipath propagation through ionized media convolves each burst with a one-sided exponential, producing a scattering tail whose timescale scales steeply with frequency, τ ∝ ν^α with α ≈ −4. An observed burst width, however, also carries contributions from intrinsic emission, instrumental sampling, residual dispersion, drift smearing, and unresolved sub-bursts, several of which produce asymmetric profiles.
        Sub-band methods have been widely used to estimate FRB scattering. Here we present a sub-band extension to the per-channel arrival-times pipeline of Chamma et al. (2025), designed to estimate scattering only where the data support it. Each profile is fit with an exponentially modified Gaussian (EMG), with an FRBs spectral bandwidth further divided into dedrifted sub-bands. The recovered tail timescales are fit with a power law, where only an index within the empirical range −4.4 ≤ α ≤ −3.6 licenses a scattering interpretation.
        As a preliminary single-burst demonstration, we apply the pipeline to FRB 20210415C from the second CHIME/FRB repeater catalogue. Seven sub-bands across 420–760 MHz yield α = −3.94 ± 0.12, consistent with thin-screen scattering. Initial tests on simulated bursts suggest the index is robust. While these results are preliminary, we estimate that the scattering tail exceeds Galactic model predictions along this sightline by ~400×, pointing to non-Galactic scattering. This work highlights the importance of further efforts to separate scattering from other broadening processes.

        Speaker: Victor Pop (McMaster University)
      • 14:18
        SN2024uwq and the Evolutionary History of Type IIb Supernovae 1m

        Yellow Supergiants have been observed exploding as Type IIb Supernovae (SNe), which is not predicted by standard single-star evolution models. The evolutionary history of these progenitors is still highly debated, however, there is tentative evidence for two Type IIb progenitor classifications – those with compact versus extended radii – which have different mass-loss histories. Early optical data, which constrains the progenitor's mass and radius, can be complemented with radio light curve data that probes the circumstellar medium (CSM) to explore the evolutionary history and properties of these progenitors. Using synchrotron self-absorption models, we perform this analysis on the nearby Type IIb supernova SN2024uwq. Further, we compare SN2024uwq to other Type IIb supernovae with early detection data and binary stellar evolution models to assess population-level trends. We determine that SN2024uwq has a wind-like CSM with a seemingly more compact progenitor, which leads to higher windspeeds in contrast to the rest of our catalogue. Comparing the evolutionary histories of these supernovae, we find that SN2024uwq may indicate that there are intermediate Type IIb Supernovae, or that the proposed extended versus compact classification is a continuum.

        Speaker: Annalisa Teixeira
      • 14:19
        The Polarization and Magnetic Field of the Radio Arc as Observed by ALMA at 100 GHz 1m

        The unique Galactic Center non-thermal filaments (NTFs) have been a focus of investigations for over 40 years. The most prominent manifestation of the NTFs is a bundle of parallel filaments known as the Radio Arc. Radio polarimetric observations made with the Very Large Array (VLA) at 10 GHz have revealed an alternating magnetic field pattern in the Radio Arc that could either be a result of multiple field systems being encountered along the line of sight or an intrinsic feature of the Radio Arc. These VLA observations were not able to distinguish between these possibilities due to the large rotation measures encountered towards the source. We present ALMA 100 GHz observations of the Radio Arc that are not impacted by significant Faraday effects. The observations reported here represent both the first time that ALMA has been used to study the NTFs and the first time 100 GHz polarimetric observations have been conducted on the Radio Arc. We find a uniformly rotated magnetic field with respect to the NTF filament orientation, with the angle of rotation being constant along the length of each filament. However, we find a systematically different magnetic field orientation in different Radio Arc filaments. We use this field pattern to update our understanding of the line-of-sight structures local to the Radio Arc. We find that the magnetic field inferred from our ALMA observations is likely a result either of confusion from multiple magnetic field systems or because the polarization is centrally concentrated within the NTF filaments.

        Speaker: Nora Salem
      • 14:20
        Inferring supernova light curves in Rubin data 1m

        The Vera C. Rubin observatory is the premier optical transient facility on sky today. Many transient sources are point sources embedded in a host galaxy. This necessitates the subtraction of that host's light before examining the brightness over time, light curve, of the transient. Standard practice is to stack images from before the transient to then subtract and reveal the changing light curve. While this is fast and fairly reliable, it is provably sub-optimal compared to fully forward modelling the scene and transient simultaneously. Here we present an AstroPhot model in JAX that does just this to extract reliable and physically realistic light curves. I will discuss the progress so far and tests to compare with difference imaging.

        Speaker: Connor Stone (University of Toronto)
      • 14:21
        BEAMS with Bias Correction: Is It Well-Calibrated? 1m

        Type Ia supernovae (SNe Ia) are important standardizable candles used to measure cosmic distances and constrain the expansion rate of the universe. A central challenge in analyzing these transients is Malmquist bias, which the Bayesian Estimation Applied to Multiple Species (BEAMS) with Bias Correction (BBC) framework aims to correct. While BBC yields unbiased cosmological constraints for small samples, its underlying BiasCor lookup table may fail to maintain performance as sample sizes scale up significantly.
        In this work, we evaluate the calibration of the BBC framework using backward simulation-based inference. We simulate surveys containing 2,000, 5,000, and 20,000 pure SNe Ia under the precise cosmological model assumed by the BBC BiasCor table. Passing these samples through the BBC pipeline, we perform Simulation-Based Calibration (SBC) to test whether the framework is properly calibrated.
        Even within this idealized setting – no sample contamination and model misspecification – we show that the BiasCor component introduces systematic overconfidence that worsens as sample size increases. Furthermore, the BiasCor correction interacts with the parameter degeneracy to underestimate uncertainty specifically along that axis rather than uniformly. As next-generation surveys like the Vera C. Rubin Observatory dramatically scale up SNe Ia datasets, these findings highlight important limitations in the current BBC pipeline and motivate the development of scalable and fully calibrated frameworks.

        Speaker: Linh Vo
      • 14:22
        The impact of nearby soil conditions on the MIST global 21-cm experiment 1m

        Global 21-cm experiments are designed to capture the sky-averaged 21-cm signal emitted by neutral hydrogen and use it to probe the conditions present during the earliest epochs of the universe. Other experiments, such as EDGES and SARAS 3, probe the signal produced during the era of cosmic dawn; however, their reported results are in tension with each other. One proposed explanation for the EDGES feature is systematic effects associated with the finite metal ground plane beneath the antenna.
        The Mapper of the Intergalactic Medium (IGM) Spin Temperature (MIST) is a global 21-cm experiment located in the radio-quiet Canadian High Arctic. MIST is designed to provide an independent probe of the cosmic dawn signal without a fixed ground plane, relying on careful electrical modeling of the soil beneath the antenna. Past work for MIST has treated the soil as laterally homogeneous and extending infinitely horizontally.
        We will present an overview of the MIST experiment, along with results from new simulations focusing on the impact of soil surface features on the recovered global signal. Three cases will be examined: individual rocks on the surface, a selection of rocks scattered across the surface, and undulating soil mimicking smooth Arctic surface conditions. Each case will be examined using soil parameter combinations spanning representative Arctic soil conditions around the antenna.
        The findings presented have applicability beyond the MIST experiment and the global 21-cm community, informing more traditional experiments about the behavior of soils beyond the edges of their ground planes.

        Speaker: Mr Francis McGee (McGill University)
      • 14:23
        The Long and Winding Equation: Symbolic Regression for Power Spectra from the Cosmic Dawn and Epoch of Reionization 1m

        The formation of first-generation stars and galaxies marks the onset of Cosmic Dawn. The Epoch of Reionization ensues when these structures emit ultraviolet light that ionizes neutral hydrogen in the universe. Although these epochs are some of the least understood, the 21 cm signal, which is emitted from the spin flip transition of neutral hydrogen's ground state, is a promising probe for them. The power spectrum, defined as the Fourier transform of the two-point correlation, measures the amplitude of this signal and can be directly obtained by radio telescopes. In this work, we aim to identify how various physical parameters influence this power spectrum by finding an interpretable, compact equation that describes it. We use AMBER, a semi-numerical code, to simulate neutral and ionized hydrogen maps between redshifts 5 and 15. We vary the physical parameters in this code and generate power spectra for each parameter set in the stated redshift range. We then apply symbolic regression, a machine-learning algorithm that computes a best-fit equation to given data. We use the PySR library that implements this algorithm and obtain the power spectrum as a function of physical parameters. Our current best-fit equations contain redshift, spatial frequency, and most physical parameters as arguments. The mean squared error of these equations is found to be of the order of 0.01 compared to AMBER’s results. This work shows an independent way of understanding how various physical effects shape the power spectrum throughout Cosmic Dawn and reionization.

        Speaker: Maria Bayder (McGill University)
      • 14:24
        Developing a Machine Learning Algorithm for Dark Matter Detection in the SuperCDMS Experiment 1m

        The nature of dark matter is among the most longstanding mysteries in physics and astronomy, with its detection potentially enabling a deeper understanding of physics beyond the standard model. One of the most promising candidates for dark matter is the weakly interacting massive particle (WIMP), which has become the subject of various dark matter searches across the world. The Super Cryogenic Dark Matter Search (SuperCDMS) experiment uses cylindrical crystals as detectors equipped with six superconducting sensors on either end that enable excellent energy resolution and sensitivity to potential dark matter masses as low as the eV scale. Determining the position information of particle detection events is made complicated by the crystal and sensor setup, making tools like machine learning ideal. My research has focused on developing a machine learning algorithm to predict position information for a set of calibration data. The model I used was trained on a Monte Carlo simulation of the detector, with a large component of my work being the application of different scaling methods to better model real data and hence produce a more accurate model. While the development of the algorithm is still ongoing, key results have been the model's success in predicting the position information of the calibration data as well as performing well when evaluated on metrics like energy prediction. In future studies, this model will be instrumental in analyzing data from the detector, which will further our understanding of dark matter, what its mass could and couldn’t be, and the limitations of superconducting detector physics.

        Speaker: Ms Lyssa Dale-Davies (University of Toronto)
      • 14:25
        Constraining Modified Gravity with the Marked Power Spectrum 1m

        The nature of cosmic acceleration remains an open question, with Modified Gravity (MG) providing an alternative to dark energy models within General Relativity. Cosmic voids are particularly sensitive tracers of MG and their two-point clustering captures higher order density field statistics. Since conventional two-point statistics are primarily dominated by overdensities, we use the marked power spectrum, which reweights the matter overdensity field to enhance information from voids. We first verify that the MG boost from COLA (COmoving Lagrangian Acceleration) simulations is comparable to that from corresponding full N-body simulations for the marked power spectrum and cross-spectrum within ~1%. We further show that this agreement holds across a range of mark definitions. Since the marked field contains non-Gaussian information, we develop a simulation-based inference (SBI) pipeline using a Neural Posterior Estimator (NPE) to constrain phenomenological MG (μ, η) and cosmological parameters (Ωm, As). We test this pipeline by performing parameter inference on 500 Lognormal Mock and 150 MGCOLA simulations. Our results demonstrate the feasibility of using the marked power spectrum within the SBI framework to constrain MG and cosmological parameters. This framework has the potential to extract additional information from underdense regions and improve MG constraints by combining CMB lensing maps with marked void statistics.

        Speaker: Amani Hussien (University of Toronto)
      • 14:26
        Lattice simulations of alpha-attractor inflation: numerical sensitivity and model comparisons 4m

        Inflation is a proposed period of accelerated expansion in the early universe, providing a mechanism for generating the primordial fluctuations that seeded cosmic structure. Many inflationary models are able to match the large-scale observations of the CMB and LSS, whilst differing in their dynamics and small-scale characteristics. Nonlinear effects could provide additional information about inflationary dynamics, motivating methods that retain nonlinear field evolution such as lattice simulations. For the theoretically well-motivated slow-roll $\alpha$-attractor models, however, the nonlinear corrections are expected to be small, making their numerical resolution challenging. We used InflationEasy to study E/T-model $\alpha$-attractor inflation, testing whether a lattice framework could resolve departures from linear theory and differences between these models, after accounting for numerical sensitivity.

        Our pipeline was validated against a published ultra-slow-roll benchmark. A numerical sensitivity study, varying spatial resolution, box size and integration parameters, identified restricted wavenumber ranges with $1\%-5\%$ numerical sensitivity in the curvature and post-inflationary scalar-induced GW spectra. A comparison of the E-model lattice results with a homogeneous-background evolution found no numerically resolved backreaction, while curvature power spectra agreed with linear theory within numerical sensitivity. A model normalisation test showed that replacing a common leading-order normalisation with model-specific normalisations reduced the observed differences in E/T-model results below numerical sensitivity.

        These results demonstrate the difficulty of resolving nonlinearity and differences between models for highly perturbative slow-roll inflationary models, and highlight the importance of numerical control and consistent model normalisation when interpreting small differences between inflationary predictions.

        Speaker: Nick Beavis (University of Toronto)
    • 14:30 → 14:45
      Bio break
    • 14:45 → 16:00
      Posters
    • 16:00 → 16:30
      Networking: Group Discussions
      • 16:00
        Discussion: CASCA Climate Survey 30m

        Ivana Damjanov

      • 16:00
        Discussion: Power and pitfalls of AI 30m

        Dennis Crabtree
        Christopher Matzner

      • 16:00
        Discussion: Science communication 30m

        Renee Hlozek

      • 16:00
        Q&A: Future Canadian collaboration with ESO 30m

        Erik Rosolowsky

      • 16:00
        Q&A: Jobs at universities versus national labs 30m

        Helen Kirk
        Allison Man

      • 16:00
        Q&A: Jobs in Industry 30m
      • 16:00
        Q&A: Postdoctoral positions in the US versus Canada 30m

        Anna O'Grady
        John Ruan

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